Mercurial > hg > truffle
view src/share/vm/gc_implementation/shared/adaptiveSizePolicy.cpp @ 15063:36e1a11a72b3
new StackIntrospection interface to allow access to stack contents
author | Lukas Stadler <lukas.stadler@oracle.com> |
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date | Fri, 11 Apr 2014 11:52:19 +0200 |
parents | 4ca6dc0799b6 |
children | 52b4284cb496 |
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/* * Copyright (c) 2004, 2013, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #include "precompiled.hpp" #include "gc_implementation/shared/adaptiveSizePolicy.hpp" #include "gc_interface/gcCause.hpp" #include "memory/collectorPolicy.hpp" #include "runtime/timer.hpp" #include "utilities/ostream.hpp" #include "utilities/workgroup.hpp" elapsedTimer AdaptiveSizePolicy::_minor_timer; elapsedTimer AdaptiveSizePolicy::_major_timer; bool AdaptiveSizePolicy::_debug_perturbation = false; // The throughput goal is implemented as // _throughput_goal = 1 - ( 1 / (1 + gc_cost_ratio)) // gc_cost_ratio is the ratio // application cost / gc cost // For example a gc_cost_ratio of 4 translates into a // throughput goal of .80 AdaptiveSizePolicy::AdaptiveSizePolicy(size_t init_eden_size, size_t init_promo_size, size_t init_survivor_size, double gc_pause_goal_sec, uint gc_cost_ratio) : _eden_size(init_eden_size), _promo_size(init_promo_size), _survivor_size(init_survivor_size), _gc_pause_goal_sec(gc_pause_goal_sec), _throughput_goal(1.0 - double(1.0 / (1.0 + (double) gc_cost_ratio))), _gc_overhead_limit_exceeded(false), _print_gc_overhead_limit_would_be_exceeded(false), _gc_overhead_limit_count(0), _latest_minor_mutator_interval_seconds(0), _threshold_tolerance_percent(1.0 + ThresholdTolerance/100.0), _young_gen_change_for_minor_throughput(0), _old_gen_change_for_major_throughput(0) { assert(AdaptiveSizePolicyGCTimeLimitThreshold > 0, "No opportunity to clear SoftReferences before GC overhead limit"); _avg_minor_pause = new AdaptivePaddedAverage(AdaptiveTimeWeight, PausePadding); _avg_minor_interval = new AdaptiveWeightedAverage(AdaptiveTimeWeight); _avg_minor_gc_cost = new AdaptiveWeightedAverage(AdaptiveTimeWeight); _avg_major_gc_cost = new AdaptiveWeightedAverage(AdaptiveTimeWeight); _avg_young_live = new AdaptiveWeightedAverage(AdaptiveSizePolicyWeight); _avg_old_live = new AdaptiveWeightedAverage(AdaptiveSizePolicyWeight); _avg_eden_live = new AdaptiveWeightedAverage(AdaptiveSizePolicyWeight); _avg_survived = new AdaptivePaddedAverage(AdaptiveSizePolicyWeight, SurvivorPadding); _avg_pretenured = new AdaptivePaddedNoZeroDevAverage( AdaptiveSizePolicyWeight, SurvivorPadding); _minor_pause_old_estimator = new LinearLeastSquareFit(AdaptiveSizePolicyWeight); _minor_pause_young_estimator = new LinearLeastSquareFit(AdaptiveSizePolicyWeight); _minor_collection_estimator = new LinearLeastSquareFit(AdaptiveSizePolicyWeight); _major_collection_estimator = new LinearLeastSquareFit(AdaptiveSizePolicyWeight); // Start the timers _minor_timer.start(); _young_gen_policy_is_ready = false; } // If the number of GC threads was set on the command line, // use it. // Else // Calculate the number of GC threads based on the number of Java threads. // Calculate the number of GC threads based on the size of the heap. // Use the larger. int AdaptiveSizePolicy::calc_default_active_workers(uintx total_workers, const uintx min_workers, uintx active_workers, uintx application_workers) { // If the user has specifically set the number of // GC threads, use them. // If the user has turned off using a dynamic number of GC threads // or the users has requested a specific number, set the active // number of workers to all the workers. uintx new_active_workers = total_workers; uintx prev_active_workers = active_workers; uintx active_workers_by_JT = 0; uintx active_workers_by_heap_size = 0; // Always use at least min_workers but use up to // GCThreadsPerJavaThreads * application threads. active_workers_by_JT = MAX2((uintx) GCWorkersPerJavaThread * application_workers, min_workers); // Choose a number of GC threads based on the current size // of the heap. This may be complicated because the size of // the heap depends on factors such as the thoughput goal. // Still a large heap should be collected by more GC threads. active_workers_by_heap_size = MAX2((size_t) 2U, Universe::heap()->capacity() / HeapSizePerGCThread); uintx max_active_workers = MAX2(active_workers_by_JT, active_workers_by_heap_size); // Limit the number of workers to the the number created, // (workers()). new_active_workers = MIN2(max_active_workers, (uintx) total_workers); // Increase GC workers instantly but decrease them more // slowly. if (new_active_workers < prev_active_workers) { new_active_workers = MAX2(min_workers, (prev_active_workers + new_active_workers) / 2); } // Check once more that the number of workers is within the limits. assert(min_workers <= total_workers, "Minimum workers not consistent with total workers"); assert(new_active_workers >= min_workers, "Minimum workers not observed"); assert(new_active_workers <= total_workers, "Total workers not observed"); if (ForceDynamicNumberOfGCThreads) { // Assume this is debugging and jiggle the number of GC threads. if (new_active_workers == prev_active_workers) { if (new_active_workers < total_workers) { new_active_workers++; } else if (new_active_workers > min_workers) { new_active_workers--; } } if (new_active_workers == total_workers) { if (_debug_perturbation) { new_active_workers = min_workers; } _debug_perturbation = !_debug_perturbation; } assert((new_active_workers <= (uintx) ParallelGCThreads) && (new_active_workers >= min_workers), "Jiggled active workers too much"); } if (TraceDynamicGCThreads) { gclog_or_tty->print_cr("GCTaskManager::calc_default_active_workers() : " "active_workers(): %d new_acitve_workers: %d " "prev_active_workers: %d\n" " active_workers_by_JT: %d active_workers_by_heap_size: %d", active_workers, new_active_workers, prev_active_workers, active_workers_by_JT, active_workers_by_heap_size); } assert(new_active_workers > 0, "Always need at least 1"); return new_active_workers; } int AdaptiveSizePolicy::calc_active_workers(uintx total_workers, uintx active_workers, uintx application_workers) { // If the user has specifically set the number of // GC threads, use them. // If the user has turned off using a dynamic number of GC threads // or the users has requested a specific number, set the active // number of workers to all the workers. int new_active_workers; if (!UseDynamicNumberOfGCThreads || (!FLAG_IS_DEFAULT(ParallelGCThreads) && !ForceDynamicNumberOfGCThreads)) { new_active_workers = total_workers; } else { new_active_workers = calc_default_active_workers(total_workers, 2, /* Minimum number of workers */ active_workers, application_workers); } assert(new_active_workers > 0, "Always need at least 1"); return new_active_workers; } int AdaptiveSizePolicy::calc_active_conc_workers(uintx total_workers, uintx active_workers, uintx application_workers) { if (!UseDynamicNumberOfGCThreads || (!FLAG_IS_DEFAULT(ConcGCThreads) && !ForceDynamicNumberOfGCThreads)) { return ConcGCThreads; } else { int no_of_gc_threads = calc_default_active_workers( total_workers, 1, /* Minimum number of workers */ active_workers, application_workers); return no_of_gc_threads; } } bool AdaptiveSizePolicy::tenuring_threshold_change() const { return decrement_tenuring_threshold_for_gc_cost() || increment_tenuring_threshold_for_gc_cost() || decrement_tenuring_threshold_for_survivor_limit(); } void AdaptiveSizePolicy::minor_collection_begin() { // Update the interval time _minor_timer.stop(); // Save most recent collection time _latest_minor_mutator_interval_seconds = _minor_timer.seconds(); _minor_timer.reset(); _minor_timer.start(); } void AdaptiveSizePolicy::update_minor_pause_young_estimator( double minor_pause_in_ms) { double eden_size_in_mbytes = ((double)_eden_size)/((double)M); _minor_pause_young_estimator->update(eden_size_in_mbytes, minor_pause_in_ms); } void AdaptiveSizePolicy::minor_collection_end(GCCause::Cause gc_cause) { // Update the pause time. _minor_timer.stop(); if (gc_cause != GCCause::_java_lang_system_gc || UseAdaptiveSizePolicyWithSystemGC) { double minor_pause_in_seconds = _minor_timer.seconds(); double minor_pause_in_ms = minor_pause_in_seconds * MILLIUNITS; // Sample for performance counter _avg_minor_pause->sample(minor_pause_in_seconds); // Cost of collection (unit-less) double collection_cost = 0.0; if ((_latest_minor_mutator_interval_seconds > 0.0) && (minor_pause_in_seconds > 0.0)) { double interval_in_seconds = _latest_minor_mutator_interval_seconds + minor_pause_in_seconds; collection_cost = minor_pause_in_seconds / interval_in_seconds; _avg_minor_gc_cost->sample(collection_cost); // Sample for performance counter _avg_minor_interval->sample(interval_in_seconds); } // The policy does not have enough data until at least some // minor collections have been done. _young_gen_policy_is_ready = (_avg_minor_gc_cost->count() >= AdaptiveSizePolicyReadyThreshold); // Calculate variables used to estimate pause time vs. gen sizes double eden_size_in_mbytes = ((double)_eden_size)/((double)M); update_minor_pause_young_estimator(minor_pause_in_ms); update_minor_pause_old_estimator(minor_pause_in_ms); if (PrintAdaptiveSizePolicy && Verbose) { gclog_or_tty->print("AdaptiveSizePolicy::minor_collection_end: " "minor gc cost: %f average: %f", collection_cost, _avg_minor_gc_cost->average()); gclog_or_tty->print_cr(" minor pause: %f minor period %f", minor_pause_in_ms, _latest_minor_mutator_interval_seconds * MILLIUNITS); } // Calculate variable used to estimate collection cost vs. gen sizes assert(collection_cost >= 0.0, "Expected to be non-negative"); _minor_collection_estimator->update(eden_size_in_mbytes, collection_cost); } // Interval times use this timer to measure the mutator time. // Reset the timer after the GC pause. _minor_timer.reset(); _minor_timer.start(); } size_t AdaptiveSizePolicy::eden_increment(size_t cur_eden, uint percent_change) { size_t eden_heap_delta; eden_heap_delta = cur_eden / 100 * percent_change; return eden_heap_delta; } size_t AdaptiveSizePolicy::eden_increment(size_t cur_eden) { return eden_increment(cur_eden, YoungGenerationSizeIncrement); } size_t AdaptiveSizePolicy::eden_decrement(size_t cur_eden) { size_t eden_heap_delta = eden_increment(cur_eden) / AdaptiveSizeDecrementScaleFactor; return eden_heap_delta; } size_t AdaptiveSizePolicy::promo_increment(size_t cur_promo, uint percent_change) { size_t promo_heap_delta; promo_heap_delta = cur_promo / 100 * percent_change; return promo_heap_delta; } size_t AdaptiveSizePolicy::promo_increment(size_t cur_promo) { return promo_increment(cur_promo, TenuredGenerationSizeIncrement); } size_t AdaptiveSizePolicy::promo_decrement(size_t cur_promo) { size_t promo_heap_delta = promo_increment(cur_promo); promo_heap_delta = promo_heap_delta / AdaptiveSizeDecrementScaleFactor; return promo_heap_delta; } double AdaptiveSizePolicy::time_since_major_gc() const { _major_timer.stop(); double result = _major_timer.seconds(); _major_timer.start(); return result; } // Linear decay of major gc cost double AdaptiveSizePolicy::decaying_major_gc_cost() const { double major_interval = major_gc_interval_average_for_decay(); double major_gc_cost_average = major_gc_cost(); double decayed_major_gc_cost = major_gc_cost_average; if(time_since_major_gc() > 0.0) { decayed_major_gc_cost = major_gc_cost() * (((double) AdaptiveSizeMajorGCDecayTimeScale) * major_interval) / time_since_major_gc(); } // The decayed cost should always be smaller than the // average cost but the vagaries of finite arithmetic could // produce a larger value in decayed_major_gc_cost so protect // against that. return MIN2(major_gc_cost_average, decayed_major_gc_cost); } // Use a value of the major gc cost that has been decayed // by the factor // // average-interval-between-major-gc * AdaptiveSizeMajorGCDecayTimeScale / // time-since-last-major-gc // // if the average-interval-between-major-gc * AdaptiveSizeMajorGCDecayTimeScale // is less than time-since-last-major-gc. // // In cases where there are initial major gc's that // are of a relatively high cost but no later major // gc's, the total gc cost can remain high because // the major gc cost remains unchanged (since there are no major // gc's). In such a situation the value of the unchanging // major gc cost can keep the mutator throughput below // the goal when in fact the major gc cost is becoming diminishingly // small. Use the decaying gc cost only to decide whether to // adjust for throughput. Using it also to determine the adjustment // to be made for throughput also seems reasonable but there is // no test case to use to decide if it is the right thing to do // don't do it yet. double AdaptiveSizePolicy::decaying_gc_cost() const { double decayed_major_gc_cost = major_gc_cost(); double avg_major_interval = major_gc_interval_average_for_decay(); if (UseAdaptiveSizeDecayMajorGCCost && (AdaptiveSizeMajorGCDecayTimeScale > 0) && (avg_major_interval > 0.00)) { double time_since_last_major_gc = time_since_major_gc(); // Decay the major gc cost? if (time_since_last_major_gc > ((double) AdaptiveSizeMajorGCDecayTimeScale) * avg_major_interval) { // Decay using the time-since-last-major-gc decayed_major_gc_cost = decaying_major_gc_cost(); if (PrintGCDetails && Verbose) { gclog_or_tty->print_cr("\ndecaying_gc_cost: major interval average:" " %f time since last major gc: %f", avg_major_interval, time_since_last_major_gc); gclog_or_tty->print_cr(" major gc cost: %f decayed major gc cost: %f", major_gc_cost(), decayed_major_gc_cost); } } } double result = MIN2(1.0, decayed_major_gc_cost + minor_gc_cost()); return result; } void AdaptiveSizePolicy::clear_generation_free_space_flags() { set_change_young_gen_for_min_pauses(0); set_change_old_gen_for_maj_pauses(0); set_change_old_gen_for_throughput(0); set_change_young_gen_for_throughput(0); set_decrease_for_footprint(0); set_decide_at_full_gc(0); } void AdaptiveSizePolicy::check_gc_overhead_limit( size_t young_live, size_t eden_live, size_t max_old_gen_size, size_t max_eden_size, bool is_full_gc, GCCause::Cause gc_cause, CollectorPolicy* collector_policy) { // Ignore explicit GC's. Exiting here does not set the flag and // does not reset the count. Updating of the averages for system // GC's is still controlled by UseAdaptiveSizePolicyWithSystemGC. if (GCCause::is_user_requested_gc(gc_cause) || GCCause::is_serviceability_requested_gc(gc_cause)) { return; } // eden_limit is the upper limit on the size of eden based on // the maximum size of the young generation and the sizes // of the survivor space. // The question being asked is whether the gc costs are high // and the space being recovered by a collection is low. // free_in_young_gen is the free space in the young generation // after a collection and promo_live is the free space in the old // generation after a collection. // // Use the minimum of the current value of the live in the // young gen or the average of the live in the young gen. // If the current value drops quickly, that should be taken // into account (i.e., don't trigger if the amount of free // space has suddenly jumped up). If the current is much // higher than the average, use the average since it represents // the longer term behavor. const size_t live_in_eden = MIN2(eden_live, (size_t) avg_eden_live()->average()); const size_t free_in_eden = max_eden_size > live_in_eden ? max_eden_size - live_in_eden : 0; const size_t free_in_old_gen = (size_t)(max_old_gen_size - avg_old_live()->average()); const size_t total_free_limit = free_in_old_gen + free_in_eden; const size_t total_mem = max_old_gen_size + max_eden_size; const double mem_free_limit = total_mem * (GCHeapFreeLimit/100.0); const double mem_free_old_limit = max_old_gen_size * (GCHeapFreeLimit/100.0); const double mem_free_eden_limit = max_eden_size * (GCHeapFreeLimit/100.0); const double gc_cost_limit = GCTimeLimit/100.0; size_t promo_limit = (size_t)(max_old_gen_size - avg_old_live()->average()); // But don't force a promo size below the current promo size. Otherwise, // the promo size will shrink for no good reason. promo_limit = MAX2(promo_limit, _promo_size); if (PrintAdaptiveSizePolicy && (Verbose || (free_in_old_gen < (size_t) mem_free_old_limit && free_in_eden < (size_t) mem_free_eden_limit))) { gclog_or_tty->print_cr( "PSAdaptiveSizePolicy::check_gc_overhead_limit:" " promo_limit: " SIZE_FORMAT " max_eden_size: " SIZE_FORMAT " total_free_limit: " SIZE_FORMAT " max_old_gen_size: " SIZE_FORMAT " max_eden_size: " SIZE_FORMAT " mem_free_limit: " SIZE_FORMAT, promo_limit, max_eden_size, total_free_limit, max_old_gen_size, max_eden_size, (size_t) mem_free_limit); } bool print_gc_overhead_limit_would_be_exceeded = false; if (is_full_gc) { if (gc_cost() > gc_cost_limit && free_in_old_gen < (size_t) mem_free_old_limit && free_in_eden < (size_t) mem_free_eden_limit) { // Collections, on average, are taking too much time, and // gc_cost() > gc_cost_limit // we have too little space available after a full gc. // total_free_limit < mem_free_limit // where // total_free_limit is the free space available in // both generations // total_mem is the total space available for allocation // in both generations (survivor spaces are not included // just as they are not included in eden_limit). // mem_free_limit is a fraction of total_mem judged to be an // acceptable amount that is still unused. // The heap can ask for the value of this variable when deciding // whether to thrown an OutOfMemory error. // Note that the gc time limit test only works for the collections // of the young gen + tenured gen and not for collections of the // permanent gen. That is because the calculation of the space // freed by the collection is the free space in the young gen + // tenured gen. // At this point the GC overhead limit is being exceeded. inc_gc_overhead_limit_count(); if (UseGCOverheadLimit) { if (gc_overhead_limit_count() >= AdaptiveSizePolicyGCTimeLimitThreshold){ // All conditions have been met for throwing an out-of-memory set_gc_overhead_limit_exceeded(true); // Avoid consecutive OOM due to the gc time limit by resetting // the counter. reset_gc_overhead_limit_count(); } else { // The required consecutive collections which exceed the // GC time limit may or may not have been reached. We // are approaching that condition and so as not to // throw an out-of-memory before all SoftRef's have been // cleared, set _should_clear_all_soft_refs in CollectorPolicy. // The clearing will be done on the next GC. bool near_limit = gc_overhead_limit_near(); if (near_limit) { collector_policy->set_should_clear_all_soft_refs(true); if (PrintGCDetails && Verbose) { gclog_or_tty->print_cr(" Nearing GC overhead limit, " "will be clearing all SoftReference"); } } } } // Set this even when the overhead limit will not // cause an out-of-memory. Diagnostic message indicating // that the overhead limit is being exceeded is sometimes // printed. print_gc_overhead_limit_would_be_exceeded = true; } else { // Did not exceed overhead limits reset_gc_overhead_limit_count(); } } if (UseGCOverheadLimit && PrintGCDetails && Verbose) { if (gc_overhead_limit_exceeded()) { gclog_or_tty->print_cr(" GC is exceeding overhead limit " "of %d%%", GCTimeLimit); reset_gc_overhead_limit_count(); } else if (print_gc_overhead_limit_would_be_exceeded) { assert(gc_overhead_limit_count() > 0, "Should not be printing"); gclog_or_tty->print_cr(" GC would exceed overhead limit " "of %d%% %d consecutive time(s)", GCTimeLimit, gc_overhead_limit_count()); } } } // Printing bool AdaptiveSizePolicy::print_adaptive_size_policy_on(outputStream* st) const { // Should only be used with adaptive size policy turned on. // Otherwise, there may be variables that are undefined. if (!UseAdaptiveSizePolicy) return false; // Print goal for which action is needed. char* action = NULL; bool change_for_pause = false; if ((change_old_gen_for_maj_pauses() == decrease_old_gen_for_maj_pauses_true) || (change_young_gen_for_min_pauses() == decrease_young_gen_for_min_pauses_true)) { action = (char*) " *** pause time goal ***"; change_for_pause = true; } else if ((change_old_gen_for_throughput() == increase_old_gen_for_throughput_true) || (change_young_gen_for_throughput() == increase_young_gen_for_througput_true)) { action = (char*) " *** throughput goal ***"; } else if (decrease_for_footprint()) { action = (char*) " *** reduced footprint ***"; } else { // No actions were taken. This can legitimately be the // situation if not enough data has been gathered to make // decisions. return false; } // Pauses // Currently the size of the old gen is only adjusted to // change the major pause times. char* young_gen_action = NULL; char* tenured_gen_action = NULL; char* shrink_msg = (char*) "(attempted to shrink)"; char* grow_msg = (char*) "(attempted to grow)"; char* no_change_msg = (char*) "(no change)"; if (change_young_gen_for_min_pauses() == decrease_young_gen_for_min_pauses_true) { young_gen_action = shrink_msg; } else if (change_for_pause) { young_gen_action = no_change_msg; } if (change_old_gen_for_maj_pauses() == decrease_old_gen_for_maj_pauses_true) { tenured_gen_action = shrink_msg; } else if (change_for_pause) { tenured_gen_action = no_change_msg; } // Throughput if (change_old_gen_for_throughput() == increase_old_gen_for_throughput_true) { assert(change_young_gen_for_throughput() == increase_young_gen_for_througput_true, "Both generations should be growing"); young_gen_action = grow_msg; tenured_gen_action = grow_msg; } else if (change_young_gen_for_throughput() == increase_young_gen_for_througput_true) { // Only the young generation may grow at start up (before // enough full collections have been done to grow the old generation). young_gen_action = grow_msg; tenured_gen_action = no_change_msg; } // Minimum footprint if (decrease_for_footprint() != 0) { young_gen_action = shrink_msg; tenured_gen_action = shrink_msg; } st->print_cr(" UseAdaptiveSizePolicy actions to meet %s", action); st->print_cr(" GC overhead (%%)"); st->print_cr(" Young generation: %7.2f\t %s", 100.0 * avg_minor_gc_cost()->average(), young_gen_action); st->print_cr(" Tenured generation: %7.2f\t %s", 100.0 * avg_major_gc_cost()->average(), tenured_gen_action); return true; } bool AdaptiveSizePolicy::print_adaptive_size_policy_on( outputStream* st, uint tenuring_threshold_arg) const { if (!AdaptiveSizePolicy::print_adaptive_size_policy_on(st)) { return false; } // Tenuring threshold bool tenuring_threshold_changed = true; if (decrement_tenuring_threshold_for_survivor_limit()) { st->print(" Tenuring threshold: (attempted to decrease to avoid" " survivor space overflow) = "); } else if (decrement_tenuring_threshold_for_gc_cost()) { st->print(" Tenuring threshold: (attempted to decrease to balance" " GC costs) = "); } else if (increment_tenuring_threshold_for_gc_cost()) { st->print(" Tenuring threshold: (attempted to increase to balance" " GC costs) = "); } else { tenuring_threshold_changed = false; assert(!tenuring_threshold_change(), "(no change was attempted)"); } if (tenuring_threshold_changed) { st->print_cr("%u", tenuring_threshold_arg); } return true; }