/* * Copyright (c) 2001, 2016, 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/g1/concurrentG1Refine.hpp" #include "gc/g1/concurrentMarkThread.inline.hpp" #include "gc/g1/g1CollectedHeap.inline.hpp" #include "gc/g1/g1CollectorPolicy.hpp" #include "gc/g1/g1ConcurrentMark.hpp" #include "gc/g1/g1IHOPControl.hpp" #include "gc/g1/g1GCPhaseTimes.hpp" #include "gc/g1/heapRegion.inline.hpp" #include "gc/g1/heapRegionRemSet.hpp" #include "gc/shared/gcPolicyCounters.hpp" #include "runtime/arguments.hpp" #include "runtime/java.hpp" #include "runtime/mutexLocker.hpp" #include "utilities/debug.hpp" #include "utilities/pair.hpp" // Different defaults for different number of GC threads // They were chosen by running GCOld and SPECjbb on debris with different // numbers of GC threads and choosing them based on the results // all the same static double rs_length_diff_defaults[] = { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 }; static double cost_per_card_ms_defaults[] = { 0.01, 0.005, 0.005, 0.003, 0.003, 0.002, 0.002, 0.0015 }; // all the same static double young_cards_per_entry_ratio_defaults[] = { 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0 }; static double cost_per_entry_ms_defaults[] = { 0.015, 0.01, 0.01, 0.008, 0.008, 0.0055, 0.0055, 0.005 }; static double cost_per_byte_ms_defaults[] = { 0.00006, 0.00003, 0.00003, 0.000015, 0.000015, 0.00001, 0.00001, 0.000009 }; // these should be pretty consistent static double constant_other_time_ms_defaults[] = { 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0 }; static double young_other_cost_per_region_ms_defaults[] = { 0.3, 0.2, 0.2, 0.15, 0.15, 0.12, 0.12, 0.1 }; static double non_young_other_cost_per_region_ms_defaults[] = { 1.0, 0.7, 0.7, 0.5, 0.5, 0.42, 0.42, 0.30 }; G1CollectorPolicy::G1CollectorPolicy() : _predictor(G1ConfidencePercent / 100.0), _recent_gc_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)), _concurrent_mark_remark_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)), _concurrent_mark_cleanup_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)), _alloc_rate_ms_seq(new TruncatedSeq(TruncatedSeqLength)), _prev_collection_pause_end_ms(0.0), _rs_length_diff_seq(new TruncatedSeq(TruncatedSeqLength)), _cost_per_card_ms_seq(new TruncatedSeq(TruncatedSeqLength)), _cost_scan_hcc_seq(new TruncatedSeq(TruncatedSeqLength)), _young_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)), _mixed_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)), _cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)), _mixed_cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)), _cost_per_byte_ms_seq(new TruncatedSeq(TruncatedSeqLength)), _cost_per_byte_ms_during_cm_seq(new TruncatedSeq(TruncatedSeqLength)), _constant_other_time_ms_seq(new TruncatedSeq(TruncatedSeqLength)), _young_other_cost_per_region_ms_seq(new TruncatedSeq(TruncatedSeqLength)), _non_young_other_cost_per_region_ms_seq( new TruncatedSeq(TruncatedSeqLength)), _pending_cards_seq(new TruncatedSeq(TruncatedSeqLength)), _rs_lengths_seq(new TruncatedSeq(TruncatedSeqLength)), _pause_time_target_ms((double) MaxGCPauseMillis), _recent_prev_end_times_for_all_gcs_sec( new TruncatedSeq(NumPrevPausesForHeuristics)), _recent_avg_pause_time_ratio(0.0), _rs_lengths_prediction(0), _max_survivor_regions(0), _eden_cset_region_length(0), _survivor_cset_region_length(0), _old_cset_region_length(0), _collection_set(NULL), _collection_set_bytes_used_before(0), // Incremental CSet attributes _inc_cset_build_state(Inactive), _inc_cset_head(NULL), _inc_cset_tail(NULL), _inc_cset_bytes_used_before(0), _inc_cset_recorded_rs_lengths(0), _inc_cset_recorded_rs_lengths_diffs(0), _inc_cset_predicted_elapsed_time_ms(0.0), _inc_cset_predicted_elapsed_time_ms_diffs(0.0), // add here any more surv rate groups _recorded_survivor_regions(0), _recorded_survivor_head(NULL), _recorded_survivor_tail(NULL), _survivors_age_table(true), _gc_overhead_perc(0.0), _bytes_allocated_in_old_since_last_gc(0), _ihop_control(NULL), _initial_mark_to_mixed() { // SurvRateGroups below must be initialized after the predictor because they // indirectly use it through this object passed to their constructor. _short_lived_surv_rate_group = new SurvRateGroup(&_predictor, "Short Lived", G1YoungSurvRateNumRegionsSummary); _survivor_surv_rate_group = new SurvRateGroup(&_predictor, "Survivor", G1YoungSurvRateNumRegionsSummary); // Set up the region size and associated fields. Given that the // policy is created before the heap, we have to set this up here, // so it's done as soon as possible. // It would have been natural to pass initial_heap_byte_size() and // max_heap_byte_size() to setup_heap_region_size() but those have // not been set up at this point since they should be aligned with // the region size. So, there is a circular dependency here. We base // the region size on the heap size, but the heap size should be // aligned with the region size. To get around this we use the // unaligned values for the heap. HeapRegion::setup_heap_region_size(InitialHeapSize, MaxHeapSize); HeapRegionRemSet::setup_remset_size(); _recent_prev_end_times_for_all_gcs_sec->add(os::elapsedTime()); _prev_collection_pause_end_ms = os::elapsedTime() * 1000.0; clear_ratio_check_data(); _phase_times = new G1GCPhaseTimes(ParallelGCThreads); int index = MIN2(ParallelGCThreads - 1, 7u); _rs_length_diff_seq->add(rs_length_diff_defaults[index]); _cost_per_card_ms_seq->add(cost_per_card_ms_defaults[index]); _cost_scan_hcc_seq->add(0.0); _young_cards_per_entry_ratio_seq->add( young_cards_per_entry_ratio_defaults[index]); _cost_per_entry_ms_seq->add(cost_per_entry_ms_defaults[index]); _cost_per_byte_ms_seq->add(cost_per_byte_ms_defaults[index]); _constant_other_time_ms_seq->add(constant_other_time_ms_defaults[index]); _young_other_cost_per_region_ms_seq->add( young_other_cost_per_region_ms_defaults[index]); _non_young_other_cost_per_region_ms_seq->add( non_young_other_cost_per_region_ms_defaults[index]); // Below, we might need to calculate the pause time target based on // the pause interval. When we do so we are going to give G1 maximum // flexibility and allow it to do pauses when it needs to. So, we'll // arrange that the pause interval to be pause time target + 1 to // ensure that a) the pause time target is maximized with respect to // the pause interval and b) we maintain the invariant that pause // time target < pause interval. If the user does not want this // maximum flexibility, they will have to set the pause interval // explicitly. // First make sure that, if either parameter is set, its value is // reasonable. if (!FLAG_IS_DEFAULT(MaxGCPauseMillis)) { if (MaxGCPauseMillis < 1) { vm_exit_during_initialization("MaxGCPauseMillis should be " "greater than 0"); } } if (!FLAG_IS_DEFAULT(GCPauseIntervalMillis)) { if (GCPauseIntervalMillis < 1) { vm_exit_during_initialization("GCPauseIntervalMillis should be " "greater than 0"); } } // Then, if the pause time target parameter was not set, set it to // the default value. if (FLAG_IS_DEFAULT(MaxGCPauseMillis)) { if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) { // The default pause time target in G1 is 200ms FLAG_SET_DEFAULT(MaxGCPauseMillis, 200); } else { // We do not allow the pause interval to be set without the // pause time target vm_exit_during_initialization("GCPauseIntervalMillis cannot be set " "without setting MaxGCPauseMillis"); } } // Then, if the interval parameter was not set, set it according to // the pause time target (this will also deal with the case when the // pause time target is the default value). if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) { FLAG_SET_DEFAULT(GCPauseIntervalMillis, MaxGCPauseMillis + 1); } // Finally, make sure that the two parameters are consistent. if (MaxGCPauseMillis >= GCPauseIntervalMillis) { char buffer[256]; jio_snprintf(buffer, 256, "MaxGCPauseMillis (%u) should be less than " "GCPauseIntervalMillis (%u)", MaxGCPauseMillis, GCPauseIntervalMillis); vm_exit_during_initialization(buffer); } double max_gc_time = (double) MaxGCPauseMillis / 1000.0; double time_slice = (double) GCPauseIntervalMillis / 1000.0; _mmu_tracker = new G1MMUTrackerQueue(time_slice, max_gc_time); // start conservatively (around 50ms is about right) _concurrent_mark_remark_times_ms->add(0.05); _concurrent_mark_cleanup_times_ms->add(0.20); _tenuring_threshold = MaxTenuringThreshold; assert(GCTimeRatio > 0, "we should have set it to a default value set_g1_gc_flags() " "if a user set it to 0"); _gc_overhead_perc = 100.0 * (1.0 / (1.0 + GCTimeRatio)); uintx reserve_perc = G1ReservePercent; // Put an artificial ceiling on this so that it's not set to a silly value. if (reserve_perc > 50) { reserve_perc = 50; warning("G1ReservePercent is set to a value that is too large, " "it's been updated to " UINTX_FORMAT, reserve_perc); } _reserve_factor = (double) reserve_perc / 100.0; // This will be set when the heap is expanded // for the first time during initialization. _reserve_regions = 0; _cset_chooser = new CollectionSetChooser(); } G1CollectorPolicy::~G1CollectorPolicy() { delete _ihop_control; } double G1CollectorPolicy::get_new_prediction(TruncatedSeq const* seq) const { return _predictor.get_new_prediction(seq); } size_t G1CollectorPolicy::get_new_size_prediction(TruncatedSeq const* seq) const { return (size_t)get_new_prediction(seq); } void G1CollectorPolicy::initialize_alignments() { _space_alignment = HeapRegion::GrainBytes; size_t card_table_alignment = CardTableRS::ct_max_alignment_constraint(); size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size(); _heap_alignment = MAX3(card_table_alignment, _space_alignment, page_size); } G1CollectorState* G1CollectorPolicy::collector_state() const { return _g1->collector_state(); } // There are three command line options related to the young gen size: // NewSize, MaxNewSize and NewRatio (There is also -Xmn, but that is // just a short form for NewSize==MaxNewSize). G1 will use its internal // heuristics to calculate the actual young gen size, so these options // basically only limit the range within which G1 can pick a young gen // size. Also, these are general options taking byte sizes. G1 will // internally work with a number of regions instead. So, some rounding // will occur. // // If nothing related to the the young gen size is set on the command // line we should allow the young gen to be between G1NewSizePercent // and G1MaxNewSizePercent of the heap size. This means that every time // the heap size changes, the limits for the young gen size will be // recalculated. // // If only -XX:NewSize is set we should use the specified value as the // minimum size for young gen. Still using G1MaxNewSizePercent of the // heap as maximum. // // If only -XX:MaxNewSize is set we should use the specified value as the // maximum size for young gen. Still using G1NewSizePercent of the heap // as minimum. // // If -XX:NewSize and -XX:MaxNewSize are both specified we use these values. // No updates when the heap size changes. There is a special case when // NewSize==MaxNewSize. This is interpreted as "fixed" and will use a // different heuristic for calculating the collection set when we do mixed // collection. // // If only -XX:NewRatio is set we should use the specified ratio of the heap // as both min and max. This will be interpreted as "fixed" just like the // NewSize==MaxNewSize case above. But we will update the min and max // every time the heap size changes. // // NewSize and MaxNewSize override NewRatio. So, NewRatio is ignored if it is // combined with either NewSize or MaxNewSize. (A warning message is printed.) class G1YoungGenSizer : public CHeapObj { private: enum SizerKind { SizerDefaults, SizerNewSizeOnly, SizerMaxNewSizeOnly, SizerMaxAndNewSize, SizerNewRatio }; SizerKind _sizer_kind; uint _min_desired_young_length; uint _max_desired_young_length; bool _adaptive_size; uint calculate_default_min_length(uint new_number_of_heap_regions); uint calculate_default_max_length(uint new_number_of_heap_regions); // Update the given values for minimum and maximum young gen length in regions // given the number of heap regions depending on the kind of sizing algorithm. void recalculate_min_max_young_length(uint number_of_heap_regions, uint* min_young_length, uint* max_young_length); public: G1YoungGenSizer(); // Calculate the maximum length of the young gen given the number of regions // depending on the sizing algorithm. uint max_young_length(uint number_of_heap_regions); void heap_size_changed(uint new_number_of_heap_regions); uint min_desired_young_length() { return _min_desired_young_length; } uint max_desired_young_length() { return _max_desired_young_length; } bool adaptive_young_list_length() const { return _adaptive_size; } }; G1YoungGenSizer::G1YoungGenSizer() : _sizer_kind(SizerDefaults), _adaptive_size(true), _min_desired_young_length(0), _max_desired_young_length(0) { if (FLAG_IS_CMDLINE(NewRatio)) { if (FLAG_IS_CMDLINE(NewSize) || FLAG_IS_CMDLINE(MaxNewSize)) { warning("-XX:NewSize and -XX:MaxNewSize override -XX:NewRatio"); } else { _sizer_kind = SizerNewRatio; _adaptive_size = false; return; } } if (NewSize > MaxNewSize) { if (FLAG_IS_CMDLINE(MaxNewSize)) { warning("NewSize (" SIZE_FORMAT "k) is greater than the MaxNewSize (" SIZE_FORMAT "k). " "A new max generation size of " SIZE_FORMAT "k will be used.", NewSize/K, MaxNewSize/K, NewSize/K); } MaxNewSize = NewSize; } if (FLAG_IS_CMDLINE(NewSize)) { _min_desired_young_length = MAX2((uint) (NewSize / HeapRegion::GrainBytes), 1U); if (FLAG_IS_CMDLINE(MaxNewSize)) { _max_desired_young_length = MAX2((uint) (MaxNewSize / HeapRegion::GrainBytes), 1U); _sizer_kind = SizerMaxAndNewSize; _adaptive_size = _min_desired_young_length == _max_desired_young_length; } else { _sizer_kind = SizerNewSizeOnly; } } else if (FLAG_IS_CMDLINE(MaxNewSize)) { _max_desired_young_length = MAX2((uint) (MaxNewSize / HeapRegion::GrainBytes), 1U); _sizer_kind = SizerMaxNewSizeOnly; } } uint G1YoungGenSizer::calculate_default_min_length(uint new_number_of_heap_regions) { uint default_value = (new_number_of_heap_regions * G1NewSizePercent) / 100; return MAX2(1U, default_value); } uint G1YoungGenSizer::calculate_default_max_length(uint new_number_of_heap_regions) { uint default_value = (new_number_of_heap_regions * G1MaxNewSizePercent) / 100; return MAX2(1U, default_value); } void G1YoungGenSizer::recalculate_min_max_young_length(uint number_of_heap_regions, uint* min_young_length, uint* max_young_length) { assert(number_of_heap_regions > 0, "Heap must be initialized"); switch (_sizer_kind) { case SizerDefaults: *min_young_length = calculate_default_min_length(number_of_heap_regions); *max_young_length = calculate_default_max_length(number_of_heap_regions); break; case SizerNewSizeOnly: *max_young_length = calculate_default_max_length(number_of_heap_regions); *max_young_length = MAX2(*min_young_length, *max_young_length); break; case SizerMaxNewSizeOnly: *min_young_length = calculate_default_min_length(number_of_heap_regions); *min_young_length = MIN2(*min_young_length, *max_young_length); break; case SizerMaxAndNewSize: // Do nothing. Values set on the command line, don't update them at runtime. break; case SizerNewRatio: *min_young_length = number_of_heap_regions / (NewRatio + 1); *max_young_length = *min_young_length; break; default: ShouldNotReachHere(); } assert(*min_young_length <= *max_young_length, "Invalid min/max young gen size values"); } uint G1YoungGenSizer::max_young_length(uint number_of_heap_regions) { // We need to pass the desired values because recalculation may not update these // values in some cases. uint temp = _min_desired_young_length; uint result = _max_desired_young_length; recalculate_min_max_young_length(number_of_heap_regions, &temp, &result); return result; } void G1YoungGenSizer::heap_size_changed(uint new_number_of_heap_regions) { recalculate_min_max_young_length(new_number_of_heap_regions, &_min_desired_young_length, &_max_desired_young_length); } void G1CollectorPolicy::post_heap_initialize() { uintx max_regions = G1CollectedHeap::heap()->max_regions(); size_t max_young_size = (size_t)_young_gen_sizer->max_young_length(max_regions) * HeapRegion::GrainBytes; if (max_young_size != MaxNewSize) { FLAG_SET_ERGO(size_t, MaxNewSize, max_young_size); } _ihop_control = create_ihop_control(); } void G1CollectorPolicy::initialize_flags() { if (G1HeapRegionSize != HeapRegion::GrainBytes) { FLAG_SET_ERGO(size_t, G1HeapRegionSize, HeapRegion::GrainBytes); } if (SurvivorRatio < 1) { vm_exit_during_initialization("Invalid survivor ratio specified"); } CollectorPolicy::initialize_flags(); _young_gen_sizer = new G1YoungGenSizer(); // Must be after call to initialize_flags } void G1CollectorPolicy::init() { // Set aside an initial future to_space. _g1 = G1CollectedHeap::heap(); assert(Heap_lock->owned_by_self(), "Locking discipline."); initialize_gc_policy_counters(); if (adaptive_young_list_length()) { _young_list_fixed_length = 0; } else { _young_list_fixed_length = _young_gen_sizer->min_desired_young_length(); } _free_regions_at_end_of_collection = _g1->num_free_regions(); update_young_list_max_and_target_length(); // We may immediately start allocating regions and placing them on the // collection set list. Initialize the per-collection set info start_incremental_cset_building(); } void G1CollectorPolicy::note_gc_start(uint num_active_workers) { phase_times()->note_gc_start(num_active_workers); } // Create the jstat counters for the policy. void G1CollectorPolicy::initialize_gc_policy_counters() { _gc_policy_counters = new GCPolicyCounters("GarbageFirst", 1, 3); } bool G1CollectorPolicy::predict_will_fit(uint young_length, double base_time_ms, uint base_free_regions, double target_pause_time_ms) const { if (young_length >= base_free_regions) { // end condition 1: not enough space for the young regions return false; } double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1); size_t bytes_to_copy = (size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes); double copy_time_ms = predict_object_copy_time_ms(bytes_to_copy); double young_other_time_ms = predict_young_other_time_ms(young_length); double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms; if (pause_time_ms > target_pause_time_ms) { // end condition 2: prediction is over the target pause time return false; } size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes; // When copying, we will likely need more bytes free than is live in the region. // Add some safety margin to factor in the confidence of our guess, and the // natural expected waste. // (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty // of the calculation: the lower the confidence, the more headroom. // (100 + TargetPLABWastePct) represents the increase in expected bytes during // copying due to anticipated waste in the PLABs. double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0; size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy); if (expected_bytes_to_copy > free_bytes) { // end condition 3: out-of-space return false; } // success! return true; } void G1CollectorPolicy::record_new_heap_size(uint new_number_of_regions) { // re-calculate the necessary reserve double reserve_regions_d = (double) new_number_of_regions * _reserve_factor; // We use ceiling so that if reserve_regions_d is > 0.0 (but // smaller than 1.0) we'll get 1. _reserve_regions = (uint) ceil(reserve_regions_d); _young_gen_sizer->heap_size_changed(new_number_of_regions); } uint G1CollectorPolicy::calculate_young_list_desired_min_length( uint base_min_length) const { uint desired_min_length = 0; if (adaptive_young_list_length()) { if (_alloc_rate_ms_seq->num() > 3) { double now_sec = os::elapsedTime(); double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0; double alloc_rate_ms = predict_alloc_rate_ms(); desired_min_length = (uint) ceil(alloc_rate_ms * when_ms); } else { // otherwise we don't have enough info to make the prediction } } desired_min_length += base_min_length; // make sure we don't go below any user-defined minimum bound return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length); } uint G1CollectorPolicy::calculate_young_list_desired_max_length() const { // Here, we might want to also take into account any additional // constraints (i.e., user-defined minimum bound). Currently, we // effectively don't set this bound. return _young_gen_sizer->max_desired_young_length(); } uint G1CollectorPolicy::update_young_list_max_and_target_length() { return update_young_list_max_and_target_length(get_new_size_prediction(_rs_lengths_seq)); } uint G1CollectorPolicy::update_young_list_max_and_target_length(size_t rs_lengths) { uint unbounded_target_length = update_young_list_target_length(rs_lengths); update_max_gc_locker_expansion(); return unbounded_target_length; } uint G1CollectorPolicy::update_young_list_target_length(size_t rs_lengths) { YoungTargetLengths young_lengths = young_list_target_lengths(rs_lengths); _young_list_target_length = young_lengths.first; return young_lengths.second; } G1CollectorPolicy::YoungTargetLengths G1CollectorPolicy::young_list_target_lengths(size_t rs_lengths) const { YoungTargetLengths result; // Calculate the absolute and desired min bounds first. // This is how many young regions we already have (currently: the survivors). uint base_min_length = recorded_survivor_regions(); uint desired_min_length = calculate_young_list_desired_min_length(base_min_length); // This is the absolute minimum young length. Ensure that we // will at least have one eden region available for allocation. uint absolute_min_length = base_min_length + MAX2(_g1->young_list()->eden_length(), (uint)1); // If we shrank the young list target it should not shrink below the current size. desired_min_length = MAX2(desired_min_length, absolute_min_length); // Calculate the absolute and desired max bounds. uint desired_max_length = calculate_young_list_desired_max_length(); uint young_list_target_length = 0; if (adaptive_young_list_length()) { if (collector_state()->gcs_are_young()) { young_list_target_length = calculate_young_list_target_length(rs_lengths, base_min_length, desired_min_length, desired_max_length); } else { // Don't calculate anything and let the code below bound it to // the desired_min_length, i.e., do the next GC as soon as // possible to maximize how many old regions we can add to it. } } else { // The user asked for a fixed young gen so we'll fix the young gen // whether the next GC is young or mixed. young_list_target_length = _young_list_fixed_length; } result.second = young_list_target_length; // We will try our best not to "eat" into the reserve. uint absolute_max_length = 0; if (_free_regions_at_end_of_collection > _reserve_regions) { absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions; } if (desired_max_length > absolute_max_length) { desired_max_length = absolute_max_length; } // Make sure we don't go over the desired max length, nor under the // desired min length. In case they clash, desired_min_length wins // which is why that test is second. if (young_list_target_length > desired_max_length) { young_list_target_length = desired_max_length; } if (young_list_target_length < desired_min_length) { young_list_target_length = desired_min_length; } assert(young_list_target_length > recorded_survivor_regions(), "we should be able to allocate at least one eden region"); assert(young_list_target_length >= absolute_min_length, "post-condition"); result.first = young_list_target_length; return result; } uint G1CollectorPolicy::calculate_young_list_target_length(size_t rs_lengths, uint base_min_length, uint desired_min_length, uint desired_max_length) const { assert(adaptive_young_list_length(), "pre-condition"); assert(collector_state()->gcs_are_young(), "only call this for young GCs"); // In case some edge-condition makes the desired max length too small... if (desired_max_length <= desired_min_length) { return desired_min_length; } // We'll adjust min_young_length and max_young_length not to include // the already allocated young regions (i.e., so they reflect the // min and max eden regions we'll allocate). The base_min_length // will be reflected in the predictions by the // survivor_regions_evac_time prediction. assert(desired_min_length > base_min_length, "invariant"); uint min_young_length = desired_min_length - base_min_length; assert(desired_max_length > base_min_length, "invariant"); uint max_young_length = desired_max_length - base_min_length; double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0; double survivor_regions_evac_time = predict_survivor_regions_evac_time(); size_t pending_cards = get_new_size_prediction(_pending_cards_seq); size_t adj_rs_lengths = rs_lengths + predict_rs_length_diff(); size_t scanned_cards = predict_young_card_num(adj_rs_lengths); double base_time_ms = predict_base_elapsed_time_ms(pending_cards, scanned_cards) + survivor_regions_evac_time; uint available_free_regions = _free_regions_at_end_of_collection; uint base_free_regions = 0; if (available_free_regions > _reserve_regions) { base_free_regions = available_free_regions - _reserve_regions; } // Here, we will make sure that the shortest young length that // makes sense fits within the target pause time. if (predict_will_fit(min_young_length, base_time_ms, base_free_regions, target_pause_time_ms)) { // The shortest young length will fit into the target pause time; // we'll now check whether the absolute maximum number of young // regions will fit in the target pause time. If not, we'll do // a binary search between min_young_length and max_young_length. if (predict_will_fit(max_young_length, base_time_ms, base_free_regions, target_pause_time_ms)) { // The maximum young length will fit into the target pause time. // We are done so set min young length to the maximum length (as // the result is assumed to be returned in min_young_length). min_young_length = max_young_length; } else { // The maximum possible number of young regions will not fit within // the target pause time so we'll search for the optimal // length. The loop invariants are: // // min_young_length < max_young_length // min_young_length is known to fit into the target pause time // max_young_length is known not to fit into the target pause time // // Going into the loop we know the above hold as we've just // checked them. Every time around the loop we check whether // the middle value between min_young_length and // max_young_length fits into the target pause time. If it // does, it becomes the new min. If it doesn't, it becomes // the new max. This way we maintain the loop invariants. assert(min_young_length < max_young_length, "invariant"); uint diff = (max_young_length - min_young_length) / 2; while (diff > 0) { uint young_length = min_young_length + diff; if (predict_will_fit(young_length, base_time_ms, base_free_regions, target_pause_time_ms)) { min_young_length = young_length; } else { max_young_length = young_length; } assert(min_young_length < max_young_length, "invariant"); diff = (max_young_length - min_young_length) / 2; } // The results is min_young_length which, according to the // loop invariants, should fit within the target pause time. // These are the post-conditions of the binary search above: assert(min_young_length < max_young_length, "otherwise we should have discovered that max_young_length " "fits into the pause target and not done the binary search"); assert(predict_will_fit(min_young_length, base_time_ms, base_free_regions, target_pause_time_ms), "min_young_length, the result of the binary search, should " "fit into the pause target"); assert(!predict_will_fit(min_young_length + 1, base_time_ms, base_free_regions, target_pause_time_ms), "min_young_length, the result of the binary search, should be " "optimal, so no larger length should fit into the pause target"); } } else { // Even the minimum length doesn't fit into the pause time // target, return it as the result nevertheless. } return base_min_length + min_young_length; } double G1CollectorPolicy::predict_survivor_regions_evac_time() const { double survivor_regions_evac_time = 0.0; for (HeapRegion * r = _recorded_survivor_head; r != NULL && r != _recorded_survivor_tail->get_next_young_region(); r = r->get_next_young_region()) { survivor_regions_evac_time += predict_region_elapsed_time_ms(r, collector_state()->gcs_are_young()); } return survivor_regions_evac_time; } void G1CollectorPolicy::revise_young_list_target_length_if_necessary() { guarantee( adaptive_young_list_length(), "should not call this otherwise" ); size_t rs_lengths = _g1->young_list()->sampled_rs_lengths(); if (rs_lengths > _rs_lengths_prediction) { // add 10% to avoid having to recalculate often size_t rs_lengths_prediction = rs_lengths * 1100 / 1000; update_rs_lengths_prediction(rs_lengths_prediction); update_young_list_max_and_target_length(rs_lengths_prediction); } } void G1CollectorPolicy::update_rs_lengths_prediction() { update_rs_lengths_prediction(get_new_size_prediction(_rs_lengths_seq)); } void G1CollectorPolicy::update_rs_lengths_prediction(size_t prediction) { if (collector_state()->gcs_are_young() && adaptive_young_list_length()) { _rs_lengths_prediction = prediction; } } #ifndef PRODUCT bool G1CollectorPolicy::verify_young_ages() { HeapRegion* head = _g1->young_list()->first_region(); return verify_young_ages(head, _short_lived_surv_rate_group); // also call verify_young_ages on any additional surv rate groups } bool G1CollectorPolicy::verify_young_ages(HeapRegion* head, SurvRateGroup *surv_rate_group) { guarantee( surv_rate_group != NULL, "pre-condition" ); const char* name = surv_rate_group->name(); bool ret = true; int prev_age = -1; for (HeapRegion* curr = head; curr != NULL; curr = curr->get_next_young_region()) { SurvRateGroup* group = curr->surv_rate_group(); if (group == NULL && !curr->is_survivor()) { log_error(gc, verify)("## %s: encountered NULL surv_rate_group", name); ret = false; } if (surv_rate_group == group) { int age = curr->age_in_surv_rate_group(); if (age < 0) { log_error(gc, verify)("## %s: encountered negative age", name); ret = false; } if (age <= prev_age) { log_error(gc, verify)("## %s: region ages are not strictly increasing (%d, %d)", name, age, prev_age); ret = false; } prev_age = age; } } return ret; } #endif // PRODUCT void G1CollectorPolicy::record_full_collection_start() { _full_collection_start_sec = os::elapsedTime(); // Release the future to-space so that it is available for compaction into. collector_state()->set_full_collection(true); } void G1CollectorPolicy::record_full_collection_end() { // Consider this like a collection pause for the purposes of allocation // since last pause. double end_sec = os::elapsedTime(); double full_gc_time_sec = end_sec - _full_collection_start_sec; double full_gc_time_ms = full_gc_time_sec * 1000.0; update_recent_gc_times(end_sec, full_gc_time_ms); collector_state()->set_full_collection(false); // "Nuke" the heuristics that control the young/mixed GC // transitions and make sure we start with young GCs after the Full GC. collector_state()->set_gcs_are_young(true); collector_state()->set_last_young_gc(false); collector_state()->set_initiate_conc_mark_if_possible(need_to_start_conc_mark("end of Full GC", 0)); collector_state()->set_during_initial_mark_pause(false); collector_state()->set_in_marking_window(false); collector_state()->set_in_marking_window_im(false); _short_lived_surv_rate_group->start_adding_regions(); // also call this on any additional surv rate groups record_survivor_regions(0, NULL, NULL); _free_regions_at_end_of_collection = _g1->num_free_regions(); // Reset survivors SurvRateGroup. _survivor_surv_rate_group->reset(); update_young_list_max_and_target_length(); update_rs_lengths_prediction(); cset_chooser()->clear(); _bytes_allocated_in_old_since_last_gc = 0; record_pause(FullGC, _full_collection_start_sec, end_sec); } void G1CollectorPolicy::record_collection_pause_start(double start_time_sec) { // We only need to do this here as the policy will only be applied // to the GC we're about to start. so, no point is calculating this // every time we calculate / recalculate the target young length. update_survivors_policy(); assert(_g1->used() == _g1->recalculate_used(), "sanity, used: " SIZE_FORMAT " recalculate_used: " SIZE_FORMAT, _g1->used(), _g1->recalculate_used()); phase_times()->record_cur_collection_start_sec(start_time_sec); _pending_cards = _g1->pending_card_num(); _collection_set_bytes_used_before = 0; _bytes_copied_during_gc = 0; collector_state()->set_last_gc_was_young(false); // do that for any other surv rate groups _short_lived_surv_rate_group->stop_adding_regions(); _survivors_age_table.clear(); assert( verify_young_ages(), "region age verification" ); } void G1CollectorPolicy::record_concurrent_mark_init_end(double mark_init_elapsed_time_ms) { collector_state()->set_during_marking(true); assert(!collector_state()->initiate_conc_mark_if_possible(), "we should have cleared it by now"); collector_state()->set_during_initial_mark_pause(false); } void G1CollectorPolicy::record_concurrent_mark_remark_start() { _mark_remark_start_sec = os::elapsedTime(); collector_state()->set_during_marking(false); } void G1CollectorPolicy::record_concurrent_mark_remark_end() { double end_time_sec = os::elapsedTime(); double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0; _concurrent_mark_remark_times_ms->add(elapsed_time_ms); _prev_collection_pause_end_ms += elapsed_time_ms; record_pause(Remark, _mark_remark_start_sec, end_time_sec); } void G1CollectorPolicy::record_concurrent_mark_cleanup_start() { _mark_cleanup_start_sec = os::elapsedTime(); } void G1CollectorPolicy::record_concurrent_mark_cleanup_completed() { bool should_continue_with_reclaim = next_gc_should_be_mixed("request last young-only gc", "skip last young-only gc"); collector_state()->set_last_young_gc(should_continue_with_reclaim); // We skip the marking phase. if (!should_continue_with_reclaim) { abort_time_to_mixed_tracking(); } collector_state()->set_in_marking_window(false); } double G1CollectorPolicy::average_time_ms(G1GCPhaseTimes::GCParPhases phase) const { return phase_times()->average_time_ms(phase); } double G1CollectorPolicy::young_other_time_ms() const { return phase_times()->young_cset_choice_time_ms() + phase_times()->young_free_cset_time_ms(); } double G1CollectorPolicy::non_young_other_time_ms() const { return phase_times()->non_young_cset_choice_time_ms() + phase_times()->non_young_free_cset_time_ms(); } double G1CollectorPolicy::other_time_ms(double pause_time_ms) const { return pause_time_ms - average_time_ms(G1GCPhaseTimes::UpdateRS) - average_time_ms(G1GCPhaseTimes::ScanRS) - average_time_ms(G1GCPhaseTimes::ObjCopy) - average_time_ms(G1GCPhaseTimes::Termination); } double G1CollectorPolicy::constant_other_time_ms(double pause_time_ms) const { return other_time_ms(pause_time_ms) - young_other_time_ms() - non_young_other_time_ms(); } bool G1CollectorPolicy::about_to_start_mixed_phase() const { return _g1->concurrent_mark()->cmThread()->during_cycle() || collector_state()->last_young_gc(); } bool G1CollectorPolicy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) { if (about_to_start_mixed_phase()) { return false; } size_t marking_initiating_used_threshold = _ihop_control->get_conc_mark_start_threshold(); size_t cur_used_bytes = _g1->non_young_capacity_bytes(); size_t alloc_byte_size = alloc_word_size * HeapWordSize; size_t marking_request_bytes = cur_used_bytes + alloc_byte_size; bool result = false; if (marking_request_bytes > marking_initiating_used_threshold) { result = collector_state()->gcs_are_young() && !collector_state()->last_young_gc(); log_debug(gc, ergo, ihop)("%s occupancy: " SIZE_FORMAT "B allocation request: " SIZE_FORMAT "B threshold: " SIZE_FORMAT "B (%1.2f) source: %s", result ? "Request concurrent cycle initiation (occupancy higher than threshold)" : "Do not request concurrent cycle initiation (still doing mixed collections)", cur_used_bytes, alloc_byte_size, marking_initiating_used_threshold, (double) marking_initiating_used_threshold / _g1->capacity() * 100, source); } return result; } // Anything below that is considered to be zero #define MIN_TIMER_GRANULARITY 0.0000001 void G1CollectorPolicy::record_collection_pause_end(double pause_time_ms, size_t cards_scanned, size_t heap_used_bytes_before_gc) { double end_time_sec = os::elapsedTime(); size_t cur_used_bytes = _g1->used(); assert(cur_used_bytes == _g1->recalculate_used(), "It should!"); bool last_pause_included_initial_mark = false; bool update_stats = !_g1->evacuation_failed(); NOT_PRODUCT(_short_lived_surv_rate_group->print()); record_pause(young_gc_pause_kind(), end_time_sec - pause_time_ms / 1000.0, end_time_sec); last_pause_included_initial_mark = collector_state()->during_initial_mark_pause(); if (last_pause_included_initial_mark) { record_concurrent_mark_init_end(0.0); } else { maybe_start_marking(); } double app_time_ms = (phase_times()->cur_collection_start_sec() * 1000.0 - _prev_collection_pause_end_ms); if (app_time_ms < MIN_TIMER_GRANULARITY) { // This usually happens due to the timer not having the required // granularity. Some Linuxes are the usual culprits. // We'll just set it to something (arbitrarily) small. app_time_ms = 1.0; } if (update_stats) { // We maintain the invariant that all objects allocated by mutator // threads will be allocated out of eden regions. So, we can use // the eden region number allocated since the previous GC to // calculate the application's allocate rate. The only exception // to that is humongous objects that are allocated separately. But // given that humongous object allocations do not really affect // either the pause's duration nor when the next pause will take // place we can safely ignore them here. uint regions_allocated = eden_cset_region_length(); double alloc_rate_ms = (double) regions_allocated / app_time_ms; _alloc_rate_ms_seq->add(alloc_rate_ms); double interval_ms = (end_time_sec - _recent_prev_end_times_for_all_gcs_sec->oldest()) * 1000.0; update_recent_gc_times(end_time_sec, pause_time_ms); _recent_avg_pause_time_ratio = _recent_gc_times_ms->sum()/interval_ms; if (recent_avg_pause_time_ratio() < 0.0 || (recent_avg_pause_time_ratio() - 1.0 > 0.0)) { // Clip ratio between 0.0 and 1.0, and continue. This will be fixed in // CR 6902692 by redoing the manner in which the ratio is incrementally computed. if (_recent_avg_pause_time_ratio < 0.0) { _recent_avg_pause_time_ratio = 0.0; } else { assert(_recent_avg_pause_time_ratio - 1.0 > 0.0, "Ctl-point invariant"); _recent_avg_pause_time_ratio = 1.0; } } // Compute the ratio of just this last pause time to the entire time range stored // in the vectors. Comparing this pause to the entire range, rather than only the // most recent interval, has the effect of smoothing over a possible transient 'burst' // of more frequent pauses that don't really reflect a change in heap occupancy. // This reduces the likelihood of a needless heap expansion being triggered. _last_pause_time_ratio = (pause_time_ms * _recent_prev_end_times_for_all_gcs_sec->num()) / interval_ms; } bool new_in_marking_window = collector_state()->in_marking_window(); bool new_in_marking_window_im = false; if (last_pause_included_initial_mark) { new_in_marking_window = true; new_in_marking_window_im = true; } if (collector_state()->last_young_gc()) { // This is supposed to to be the "last young GC" before we start // doing mixed GCs. Here we decide whether to start mixed GCs or not. assert(!last_pause_included_initial_mark, "The last young GC is not allowed to be an initial mark GC"); if (next_gc_should_be_mixed("start mixed GCs", "do not start mixed GCs")) { collector_state()->set_gcs_are_young(false); } else { // We aborted the mixed GC phase early. abort_time_to_mixed_tracking(); } collector_state()->set_last_young_gc(false); } if (!collector_state()->last_gc_was_young()) { // This is a mixed GC. Here we decide whether to continue doing // mixed GCs or not. if (!next_gc_should_be_mixed("continue mixed GCs", "do not continue mixed GCs")) { collector_state()->set_gcs_are_young(true); maybe_start_marking(); } } _short_lived_surv_rate_group->start_adding_regions(); // Do that for any other surv rate groups double scan_hcc_time_ms = ConcurrentG1Refine::hot_card_cache_enabled() ? average_time_ms(G1GCPhaseTimes::ScanHCC) : 0.0; if (update_stats) { double cost_per_card_ms = 0.0; if (_pending_cards > 0) { cost_per_card_ms = (average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms) / (double) _pending_cards; _cost_per_card_ms_seq->add(cost_per_card_ms); } _cost_scan_hcc_seq->add(scan_hcc_time_ms); double cost_per_entry_ms = 0.0; if (cards_scanned > 10) { cost_per_entry_ms = average_time_ms(G1GCPhaseTimes::ScanRS) / (double) cards_scanned; if (collector_state()->last_gc_was_young()) { _cost_per_entry_ms_seq->add(cost_per_entry_ms); } else { _mixed_cost_per_entry_ms_seq->add(cost_per_entry_ms); } } if (_max_rs_lengths > 0) { double cards_per_entry_ratio = (double) cards_scanned / (double) _max_rs_lengths; if (collector_state()->last_gc_was_young()) { _young_cards_per_entry_ratio_seq->add(cards_per_entry_ratio); } else { _mixed_cards_per_entry_ratio_seq->add(cards_per_entry_ratio); } } // This is defensive. For a while _max_rs_lengths could get // smaller than _recorded_rs_lengths which was causing // rs_length_diff to get very large and mess up the RSet length // predictions. The reason was unsafe concurrent updates to the // _inc_cset_recorded_rs_lengths field which the code below guards // against (see CR 7118202). This bug has now been fixed (see CR // 7119027). However, I'm still worried that // _inc_cset_recorded_rs_lengths might still end up somewhat // inaccurate. The concurrent refinement thread calculates an // RSet's length concurrently with other CR threads updating it // which might cause it to calculate the length incorrectly (if, // say, it's in mid-coarsening). So I'll leave in the defensive // conditional below just in case. size_t rs_length_diff = 0; if (_max_rs_lengths > _recorded_rs_lengths) { rs_length_diff = _max_rs_lengths - _recorded_rs_lengths; } _rs_length_diff_seq->add((double) rs_length_diff); size_t freed_bytes = heap_used_bytes_before_gc - cur_used_bytes; size_t copied_bytes = _collection_set_bytes_used_before - freed_bytes; double cost_per_byte_ms = 0.0; if (copied_bytes > 0) { cost_per_byte_ms = average_time_ms(G1GCPhaseTimes::ObjCopy) / (double) copied_bytes; if (collector_state()->in_marking_window()) { _cost_per_byte_ms_during_cm_seq->add(cost_per_byte_ms); } else { _cost_per_byte_ms_seq->add(cost_per_byte_ms); } } if (young_cset_region_length() > 0) { _young_other_cost_per_region_ms_seq->add(young_other_time_ms() / young_cset_region_length()); } if (old_cset_region_length() > 0) { _non_young_other_cost_per_region_ms_seq->add(non_young_other_time_ms() / old_cset_region_length()); } _constant_other_time_ms_seq->add(constant_other_time_ms(pause_time_ms)); _pending_cards_seq->add((double) _pending_cards); _rs_lengths_seq->add((double) _max_rs_lengths); } collector_state()->set_in_marking_window(new_in_marking_window); collector_state()->set_in_marking_window_im(new_in_marking_window_im); _free_regions_at_end_of_collection = _g1->num_free_regions(); // IHOP control wants to know the expected young gen length if it were not // restrained by the heap reserve. Using the actual length would make the // prediction too small and the limit the young gen every time we get to the // predicted target occupancy. size_t last_unrestrained_young_length = update_young_list_max_and_target_length(); update_rs_lengths_prediction(); update_ihop_prediction(app_time_ms / 1000.0, _bytes_allocated_in_old_since_last_gc, last_unrestrained_young_length * HeapRegion::GrainBytes); _bytes_allocated_in_old_since_last_gc = 0; _ihop_control->send_trace_event(_g1->gc_tracer_stw()); // Note that _mmu_tracker->max_gc_time() returns the time in seconds. double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0; if (update_rs_time_goal_ms < scan_hcc_time_ms) { log_debug(gc, ergo, refine)("Adjust concurrent refinement thresholds (scanning the HCC expected to take longer than Update RS time goal)." "Update RS time goal: %1.2fms Scan HCC time: %1.2fms", update_rs_time_goal_ms, scan_hcc_time_ms); update_rs_time_goal_ms = 0; } else { update_rs_time_goal_ms -= scan_hcc_time_ms; } adjust_concurrent_refinement(average_time_ms(G1GCPhaseTimes::UpdateRS) - scan_hcc_time_ms, phase_times()->sum_thread_work_items(G1GCPhaseTimes::UpdateRS), update_rs_time_goal_ms); cset_chooser()->verify(); } G1IHOPControl* G1CollectorPolicy::create_ihop_control() const { if (G1UseAdaptiveIHOP) { return new G1AdaptiveIHOPControl(InitiatingHeapOccupancyPercent, G1CollectedHeap::heap()->max_capacity(), &_predictor, G1ReservePercent, G1HeapWastePercent); } else { return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent, G1CollectedHeap::heap()->max_capacity()); } } void G1CollectorPolicy::update_ihop_prediction(double mutator_time_s, size_t mutator_alloc_bytes, size_t young_gen_size) { // Always try to update IHOP prediction. Even evacuation failures give information // about e.g. whether to start IHOP earlier next time. // Avoid using really small application times that might create samples with // very high or very low values. They may be caused by e.g. back-to-back gcs. double const min_valid_time = 1e-6; bool report = false; double marking_to_mixed_time = -1.0; if (!collector_state()->last_gc_was_young() && _initial_mark_to_mixed.has_result()) { marking_to_mixed_time = _initial_mark_to_mixed.last_marking_time(); assert(marking_to_mixed_time > 0.0, "Initial mark to mixed time must be larger than zero but is %.3f", marking_to_mixed_time); if (marking_to_mixed_time > min_valid_time) { _ihop_control->update_marking_length(marking_to_mixed_time); report = true; } } // As an approximation for the young gc promotion rates during marking we use // all of them. In many applications there are only a few if any young gcs during // marking, which makes any prediction useless. This increases the accuracy of the // prediction. if (collector_state()->last_gc_was_young() && mutator_time_s > min_valid_time) { _ihop_control->update_allocation_info(mutator_time_s, mutator_alloc_bytes, young_gen_size); report = true; } if (report) { report_ihop_statistics(); } } void G1CollectorPolicy::report_ihop_statistics() { _ihop_control->print(); } void G1CollectorPolicy::print_phases() { phase_times()->print(); } void G1CollectorPolicy::adjust_concurrent_refinement(double update_rs_time, double update_rs_processed_buffers, double goal_ms) { DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set(); ConcurrentG1Refine *cg1r = G1CollectedHeap::heap()->concurrent_g1_refine(); if (G1UseAdaptiveConcRefinement) { const int k_gy = 3, k_gr = 6; const double inc_k = 1.1, dec_k = 0.9; int g = cg1r->green_zone(); if (update_rs_time > goal_ms) { g = (int)(g * dec_k); // Can become 0, that's OK. That would mean a mutator-only processing. } else { if (update_rs_time < goal_ms && update_rs_processed_buffers > g) { g = (int)MAX2(g * inc_k, g + 1.0); } } // Change the refinement threads params cg1r->set_green_zone(g); cg1r->set_yellow_zone(g * k_gy); cg1r->set_red_zone(g * k_gr); cg1r->reinitialize_threads(); int processing_threshold_delta = MAX2((int)(cg1r->green_zone() * _predictor.sigma()), 1); int processing_threshold = MIN2(cg1r->green_zone() + processing_threshold_delta, cg1r->yellow_zone()); // Change the barrier params dcqs.set_process_completed_threshold(processing_threshold); dcqs.set_max_completed_queue(cg1r->red_zone()); } int curr_queue_size = dcqs.completed_buffers_num(); if (curr_queue_size >= cg1r->yellow_zone()) { dcqs.set_completed_queue_padding(curr_queue_size); } else { dcqs.set_completed_queue_padding(0); } dcqs.notify_if_necessary(); } size_t G1CollectorPolicy::predict_rs_length_diff() const { return get_new_size_prediction(_rs_length_diff_seq); } double G1CollectorPolicy::predict_alloc_rate_ms() const { return get_new_prediction(_alloc_rate_ms_seq); } double G1CollectorPolicy::predict_cost_per_card_ms() const { return get_new_prediction(_cost_per_card_ms_seq); } double G1CollectorPolicy::predict_scan_hcc_ms() const { return get_new_prediction(_cost_scan_hcc_seq); } double G1CollectorPolicy::predict_rs_update_time_ms(size_t pending_cards) const { return pending_cards * predict_cost_per_card_ms() + predict_scan_hcc_ms(); } double G1CollectorPolicy::predict_young_cards_per_entry_ratio() const { return get_new_prediction(_young_cards_per_entry_ratio_seq); } double G1CollectorPolicy::predict_mixed_cards_per_entry_ratio() const { if (_mixed_cards_per_entry_ratio_seq->num() < 2) { return predict_young_cards_per_entry_ratio(); } else { return get_new_prediction(_mixed_cards_per_entry_ratio_seq); } } size_t G1CollectorPolicy::predict_young_card_num(size_t rs_length) const { return (size_t) (rs_length * predict_young_cards_per_entry_ratio()); } size_t G1CollectorPolicy::predict_non_young_card_num(size_t rs_length) const { return (size_t)(rs_length * predict_mixed_cards_per_entry_ratio()); } double G1CollectorPolicy::predict_rs_scan_time_ms(size_t card_num) const { if (collector_state()->gcs_are_young()) { return card_num * get_new_prediction(_cost_per_entry_ms_seq); } else { return predict_mixed_rs_scan_time_ms(card_num); } } double G1CollectorPolicy::predict_mixed_rs_scan_time_ms(size_t card_num) const { if (_mixed_cost_per_entry_ms_seq->num() < 3) { return card_num * get_new_prediction(_cost_per_entry_ms_seq); } else { return card_num * get_new_prediction(_mixed_cost_per_entry_ms_seq); } } double G1CollectorPolicy::predict_object_copy_time_ms_during_cm(size_t bytes_to_copy) const { if (_cost_per_byte_ms_during_cm_seq->num() < 3) { return (1.1 * bytes_to_copy) * get_new_prediction(_cost_per_byte_ms_seq); } else { return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_during_cm_seq); } } double G1CollectorPolicy::predict_object_copy_time_ms(size_t bytes_to_copy) const { if (collector_state()->during_concurrent_mark()) { return predict_object_copy_time_ms_during_cm(bytes_to_copy); } else { return bytes_to_copy * get_new_prediction(_cost_per_byte_ms_seq); } } double G1CollectorPolicy::predict_constant_other_time_ms() const { return get_new_prediction(_constant_other_time_ms_seq); } double G1CollectorPolicy::predict_young_other_time_ms(size_t young_num) const { return young_num * get_new_prediction(_young_other_cost_per_region_ms_seq); } double G1CollectorPolicy::predict_non_young_other_time_ms(size_t non_young_num) const { return non_young_num * get_new_prediction(_non_young_other_cost_per_region_ms_seq); } double G1CollectorPolicy::predict_remark_time_ms() const { return get_new_prediction(_concurrent_mark_remark_times_ms); } double G1CollectorPolicy::predict_cleanup_time_ms() const { return get_new_prediction(_concurrent_mark_cleanup_times_ms); } double G1CollectorPolicy::predict_yg_surv_rate(int age, SurvRateGroup* surv_rate_group) const { TruncatedSeq* seq = surv_rate_group->get_seq(age); guarantee(seq->num() > 0, "There should be some young gen survivor samples available. Tried to access with age %d", age); double pred = get_new_prediction(seq); if (pred > 1.0) { pred = 1.0; } return pred; } double G1CollectorPolicy::predict_yg_surv_rate(int age) const { return predict_yg_surv_rate(age, _short_lived_surv_rate_group); } double G1CollectorPolicy::accum_yg_surv_rate_pred(int age) const { return _short_lived_surv_rate_group->accum_surv_rate_pred(age); } double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards, size_t scanned_cards) const { return predict_rs_update_time_ms(pending_cards) + predict_rs_scan_time_ms(scanned_cards) + predict_constant_other_time_ms(); } double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards) const { size_t rs_length = predict_rs_length_diff(); size_t card_num; if (collector_state()->gcs_are_young()) { card_num = predict_young_card_num(rs_length); } else { card_num = predict_non_young_card_num(rs_length); } return predict_base_elapsed_time_ms(pending_cards, card_num); } size_t G1CollectorPolicy::predict_bytes_to_copy(HeapRegion* hr) const { size_t bytes_to_copy; if (hr->is_marked()) bytes_to_copy = hr->max_live_bytes(); else { assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant"); int age = hr->age_in_surv_rate_group(); double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group()); bytes_to_copy = (size_t) (hr->used() * yg_surv_rate); } return bytes_to_copy; } double G1CollectorPolicy::predict_region_elapsed_time_ms(HeapRegion* hr, bool for_young_gc) const { size_t rs_length = hr->rem_set()->occupied(); size_t card_num; // Predicting the number of cards is based on which type of GC // we're predicting for. if (for_young_gc) { card_num = predict_young_card_num(rs_length); } else { card_num = predict_non_young_card_num(rs_length); } size_t bytes_to_copy = predict_bytes_to_copy(hr); double region_elapsed_time_ms = predict_rs_scan_time_ms(card_num) + predict_object_copy_time_ms(bytes_to_copy); // The prediction of the "other" time for this region is based // upon the region type and NOT the GC type. if (hr->is_young()) { region_elapsed_time_ms += predict_young_other_time_ms(1); } else { region_elapsed_time_ms += predict_non_young_other_time_ms(1); } return region_elapsed_time_ms; } void G1CollectorPolicy::init_cset_region_lengths(uint eden_cset_region_length, uint survivor_cset_region_length) { _eden_cset_region_length = eden_cset_region_length; _survivor_cset_region_length = survivor_cset_region_length; _old_cset_region_length = 0; } void G1CollectorPolicy::set_recorded_rs_lengths(size_t rs_lengths) { _recorded_rs_lengths = rs_lengths; } void G1CollectorPolicy::update_recent_gc_times(double end_time_sec, double elapsed_ms) { _recent_gc_times_ms->add(elapsed_ms); _recent_prev_end_times_for_all_gcs_sec->add(end_time_sec); _prev_collection_pause_end_ms = end_time_sec * 1000.0; } void G1CollectorPolicy::clear_ratio_check_data() { _ratio_over_threshold_count = 0; _ratio_over_threshold_sum = 0.0; _pauses_since_start = 0; } size_t G1CollectorPolicy::expansion_amount() { double recent_gc_overhead = recent_avg_pause_time_ratio() * 100.0; double last_gc_overhead = _last_pause_time_ratio * 100.0; double threshold = _gc_overhead_perc; size_t expand_bytes = 0; // If the heap is at less than half its maximum size, scale the threshold down, // to a limit of 1. Thus the smaller the heap is, the more likely it is to expand, // though the scaling code will likely keep the increase small. if (_g1->capacity() <= _g1->max_capacity() / 2) { threshold *= (double)_g1->capacity() / (double)(_g1->max_capacity() / 2); threshold = MAX2(threshold, 1.0); } // If the last GC time ratio is over the threshold, increment the count of // times it has been exceeded, and add this ratio to the sum of exceeded // ratios. if (last_gc_overhead > threshold) { _ratio_over_threshold_count++; _ratio_over_threshold_sum += last_gc_overhead; } // Check if we've had enough GC time ratio checks that were over the // threshold to trigger an expansion. We'll also expand if we've // reached the end of the history buffer and the average of all entries // is still over the threshold. This indicates a smaller number of GCs were // long enough to make the average exceed the threshold. bool filled_history_buffer = _pauses_since_start == NumPrevPausesForHeuristics; if ((_ratio_over_threshold_count == MinOverThresholdForGrowth) || (filled_history_buffer && (recent_gc_overhead > threshold))) { size_t min_expand_bytes = HeapRegion::GrainBytes; size_t reserved_bytes = _g1->max_capacity(); size_t committed_bytes = _g1->capacity(); size_t uncommitted_bytes = reserved_bytes - committed_bytes; size_t expand_bytes_via_pct = uncommitted_bytes * G1ExpandByPercentOfAvailable / 100; double scale_factor = 1.0; // If the current size is less than 1/4 of the Initial heap size, expand // by half of the delta between the current and Initial sizes. IE, grow // back quickly. // // Otherwise, take the current size, or G1ExpandByPercentOfAvailable % of // the available expansion space, whichever is smaller, as the base // expansion size. Then possibly scale this size according to how much the // threshold has (on average) been exceeded by. If the delta is small // (less than the StartScaleDownAt value), scale the size down linearly, but // not by less than MinScaleDownFactor. If the delta is large (greater than // the StartScaleUpAt value), scale up, but adding no more than MaxScaleUpFactor // times the base size. The scaling will be linear in the range from // StartScaleUpAt to (StartScaleUpAt + ScaleUpRange). In other words, // ScaleUpRange sets the rate of scaling up. if (committed_bytes < InitialHeapSize / 4) { expand_bytes = (InitialHeapSize - committed_bytes) / 2; } else { double const MinScaleDownFactor = 0.2; double const MaxScaleUpFactor = 2; double const StartScaleDownAt = _gc_overhead_perc; double const StartScaleUpAt = _gc_overhead_perc * 1.5; double const ScaleUpRange = _gc_overhead_perc * 2.0; double ratio_delta; if (filled_history_buffer) { ratio_delta = recent_gc_overhead - threshold; } else { ratio_delta = (_ratio_over_threshold_sum/_ratio_over_threshold_count) - threshold; } expand_bytes = MIN2(expand_bytes_via_pct, committed_bytes); if (ratio_delta < StartScaleDownAt) { scale_factor = ratio_delta / StartScaleDownAt; scale_factor = MAX2(scale_factor, MinScaleDownFactor); } else if (ratio_delta > StartScaleUpAt) { scale_factor = 1 + ((ratio_delta - StartScaleUpAt) / ScaleUpRange); scale_factor = MIN2(scale_factor, MaxScaleUpFactor); } } log_debug(gc, ergo, heap)("Attempt heap expansion (recent GC overhead higher than threshold after GC) " "recent GC overhead: %1.2f %% threshold: %1.2f %% uncommitted: " SIZE_FORMAT "B base expansion amount and scale: " SIZE_FORMAT "B (%1.2f%%)", recent_gc_overhead, threshold, uncommitted_bytes, expand_bytes, scale_factor * 100); expand_bytes = static_cast(expand_bytes * scale_factor); // Ensure the expansion size is at least the minimum growth amount // and at most the remaining uncommitted byte size. expand_bytes = MAX2(expand_bytes, min_expand_bytes); expand_bytes = MIN2(expand_bytes, uncommitted_bytes); clear_ratio_check_data(); } else { // An expansion was not triggered. If we've started counting, increment // the number of checks we've made in the current window. If we've // reached the end of the window without resizing, clear the counters to // start again the next time we see a ratio above the threshold. if (_ratio_over_threshold_count > 0) { _pauses_since_start++; if (_pauses_since_start > NumPrevPausesForHeuristics) { clear_ratio_check_data(); } } } return expand_bytes; } void G1CollectorPolicy::print_yg_surv_rate_info() const { #ifndef PRODUCT _short_lived_surv_rate_group->print_surv_rate_summary(); // add this call for any other surv rate groups #endif // PRODUCT } bool G1CollectorPolicy::is_young_list_full() const { uint young_list_length = _g1->young_list()->length(); uint young_list_target_length = _young_list_target_length; return young_list_length >= young_list_target_length; } bool G1CollectorPolicy::can_expand_young_list() const { uint young_list_length = _g1->young_list()->length(); uint young_list_max_length = _young_list_max_length; return young_list_length < young_list_max_length; } bool G1CollectorPolicy::adaptive_young_list_length() const { return _young_gen_sizer->adaptive_young_list_length(); } void G1CollectorPolicy::update_max_gc_locker_expansion() { uint expansion_region_num = 0; if (GCLockerEdenExpansionPercent > 0) { double perc = (double) GCLockerEdenExpansionPercent / 100.0; double expansion_region_num_d = perc * (double) _young_list_target_length; // We use ceiling so that if expansion_region_num_d is > 0.0 (but // less than 1.0) we'll get 1. expansion_region_num = (uint) ceil(expansion_region_num_d); } else { assert(expansion_region_num == 0, "sanity"); } _young_list_max_length = _young_list_target_length + expansion_region_num; assert(_young_list_target_length <= _young_list_max_length, "post-condition"); } // Calculates survivor space parameters. void G1CollectorPolicy::update_survivors_policy() { double max_survivor_regions_d = (double) _young_list_target_length / (double) SurvivorRatio; // We use ceiling so that if max_survivor_regions_d is > 0.0 (but // smaller than 1.0) we'll get 1. _max_survivor_regions = (uint) ceil(max_survivor_regions_d); _tenuring_threshold = _survivors_age_table.compute_tenuring_threshold( HeapRegion::GrainWords * _max_survivor_regions, counters()); } bool G1CollectorPolicy::force_initial_mark_if_outside_cycle(GCCause::Cause gc_cause) { // We actually check whether we are marking here and not if we are in a // reclamation phase. This means that we will schedule a concurrent mark // even while we are still in the process of reclaiming memory. bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle(); if (!during_cycle) { log_debug(gc, ergo)("Request concurrent cycle initiation (requested by GC cause). GC cause: %s", GCCause::to_string(gc_cause)); collector_state()->set_initiate_conc_mark_if_possible(true); return true; } else { log_debug(gc, ergo)("Do not request concurrent cycle initiation (concurrent cycle already in progress). GC cause: %s", GCCause::to_string(gc_cause)); return false; } } void G1CollectorPolicy::initiate_conc_mark() { collector_state()->set_during_initial_mark_pause(true); collector_state()->set_initiate_conc_mark_if_possible(false); } void G1CollectorPolicy::decide_on_conc_mark_initiation() { // We are about to decide on whether this pause will be an // initial-mark pause. // First, collector_state()->during_initial_mark_pause() should not be already set. We // will set it here if we have to. However, it should be cleared by // the end of the pause (it's only set for the duration of an // initial-mark pause). assert(!collector_state()->during_initial_mark_pause(), "pre-condition"); if (collector_state()->initiate_conc_mark_if_possible()) { // We had noticed on a previous pause that the heap occupancy has // gone over the initiating threshold and we should start a // concurrent marking cycle. So we might initiate one. if (!about_to_start_mixed_phase() && collector_state()->gcs_are_young()) { // Initiate a new initial mark if there is no marking or reclamation going on. initiate_conc_mark(); log_debug(gc, ergo)("Initiate concurrent cycle (concurrent cycle initiation requested)"); } else if (_g1->is_user_requested_concurrent_full_gc(_g1->gc_cause())) { // Initiate a user requested initial mark. An initial mark must be young only // GC, so the collector state must be updated to reflect this. collector_state()->set_gcs_are_young(true); collector_state()->set_last_young_gc(false); abort_time_to_mixed_tracking(); initiate_conc_mark(); log_debug(gc, ergo)("Initiate concurrent cycle (user requested concurrent cycle)"); } else { // The concurrent marking thread is still finishing up the // previous cycle. If we start one right now the two cycles // overlap. In particular, the concurrent marking thread might // be in the process of clearing the next marking bitmap (which // we will use for the next cycle if we start one). Starting a // cycle now will be bad given that parts of the marking // information might get cleared by the marking thread. And we // cannot wait for the marking thread to finish the cycle as it // periodically yields while clearing the next marking bitmap // and, if it's in a yield point, it's waiting for us to // finish. So, at this point we will not start a cycle and we'll // let the concurrent marking thread complete the last one. log_debug(gc, ergo)("Do not initiate concurrent cycle (concurrent cycle already in progress)"); } } } class ParKnownGarbageHRClosure: public HeapRegionClosure { G1CollectedHeap* _g1h; CSetChooserParUpdater _cset_updater; public: ParKnownGarbageHRClosure(CollectionSetChooser* hrSorted, uint chunk_size) : _g1h(G1CollectedHeap::heap()), _cset_updater(hrSorted, true /* parallel */, chunk_size) { } bool doHeapRegion(HeapRegion* r) { // Do we have any marking information for this region? if (r->is_marked()) { // We will skip any region that's currently used as an old GC // alloc region (we should not consider those for collection // before we fill them up). if (_cset_updater.should_add(r) && !_g1h->is_old_gc_alloc_region(r)) { _cset_updater.add_region(r); } } return false; } }; class ParKnownGarbageTask: public AbstractGangTask { CollectionSetChooser* _hrSorted; uint _chunk_size; G1CollectedHeap* _g1; HeapRegionClaimer _hrclaimer; public: ParKnownGarbageTask(CollectionSetChooser* hrSorted, uint chunk_size, uint n_workers) : AbstractGangTask("ParKnownGarbageTask"), _hrSorted(hrSorted), _chunk_size(chunk_size), _g1(G1CollectedHeap::heap()), _hrclaimer(n_workers) {} void work(uint worker_id) { ParKnownGarbageHRClosure parKnownGarbageCl(_hrSorted, _chunk_size); _g1->heap_region_par_iterate(&parKnownGarbageCl, worker_id, &_hrclaimer); } }; uint G1CollectorPolicy::calculate_parallel_work_chunk_size(uint n_workers, uint n_regions) const { assert(n_workers > 0, "Active gc workers should be greater than 0"); const uint overpartition_factor = 4; const uint min_chunk_size = MAX2(n_regions / n_workers, 1U); return MAX2(n_regions / (n_workers * overpartition_factor), min_chunk_size); } void G1CollectorPolicy::record_concurrent_mark_cleanup_end() { cset_chooser()->clear(); WorkGang* workers = _g1->workers(); uint n_workers = workers->active_workers(); uint n_regions = _g1->num_regions(); uint chunk_size = calculate_parallel_work_chunk_size(n_workers, n_regions); cset_chooser()->prepare_for_par_region_addition(n_workers, n_regions, chunk_size); ParKnownGarbageTask par_known_garbage_task(cset_chooser(), chunk_size, n_workers); workers->run_task(&par_known_garbage_task); cset_chooser()->sort_regions(); double end_sec = os::elapsedTime(); double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0; _concurrent_mark_cleanup_times_ms->add(elapsed_time_ms); _prev_collection_pause_end_ms += elapsed_time_ms; record_pause(Cleanup, _mark_cleanup_start_sec, end_sec); } // Add the heap region at the head of the non-incremental collection set void G1CollectorPolicy::add_old_region_to_cset(HeapRegion* hr) { assert(_inc_cset_build_state == Active, "Precondition"); assert(hr->is_old(), "the region should be old"); assert(!hr->in_collection_set(), "should not already be in the CSet"); _g1->register_old_region_with_cset(hr); hr->set_next_in_collection_set(_collection_set); _collection_set = hr; _collection_set_bytes_used_before += hr->used(); size_t rs_length = hr->rem_set()->occupied(); _recorded_rs_lengths += rs_length; _old_cset_region_length += 1; } // Initialize the per-collection-set information void G1CollectorPolicy::start_incremental_cset_building() { assert(_inc_cset_build_state == Inactive, "Precondition"); _inc_cset_head = NULL; _inc_cset_tail = NULL; _inc_cset_bytes_used_before = 0; _inc_cset_recorded_rs_lengths = 0; _inc_cset_recorded_rs_lengths_diffs = 0; _inc_cset_predicted_elapsed_time_ms = 0.0; _inc_cset_predicted_elapsed_time_ms_diffs = 0.0; _inc_cset_build_state = Active; } void G1CollectorPolicy::finalize_incremental_cset_building() { assert(_inc_cset_build_state == Active, "Precondition"); assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint"); // The two "main" fields, _inc_cset_recorded_rs_lengths and // _inc_cset_predicted_elapsed_time_ms, are updated by the thread // that adds a new region to the CSet. Further updates by the // concurrent refinement thread that samples the young RSet lengths // are accumulated in the *_diffs fields. Here we add the diffs to // the "main" fields. if (_inc_cset_recorded_rs_lengths_diffs >= 0) { _inc_cset_recorded_rs_lengths += _inc_cset_recorded_rs_lengths_diffs; } else { // This is defensive. The diff should in theory be always positive // as RSets can only grow between GCs. However, given that we // sample their size concurrently with other threads updating them // it's possible that we might get the wrong size back, which // could make the calculations somewhat inaccurate. size_t diffs = (size_t) (-_inc_cset_recorded_rs_lengths_diffs); if (_inc_cset_recorded_rs_lengths >= diffs) { _inc_cset_recorded_rs_lengths -= diffs; } else { _inc_cset_recorded_rs_lengths = 0; } } _inc_cset_predicted_elapsed_time_ms += _inc_cset_predicted_elapsed_time_ms_diffs; _inc_cset_recorded_rs_lengths_diffs = 0; _inc_cset_predicted_elapsed_time_ms_diffs = 0.0; } void G1CollectorPolicy::add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length) { // This routine is used when: // * adding survivor regions to the incremental cset at the end of an // evacuation pause, // * adding the current allocation region to the incremental cset // when it is retired, and // * updating existing policy information for a region in the // incremental cset via young list RSet sampling. // Therefore this routine may be called at a safepoint by the // VM thread, or in-between safepoints by mutator threads (when // retiring the current allocation region) or a concurrent // refine thread (RSet sampling). double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young()); size_t used_bytes = hr->used(); _inc_cset_recorded_rs_lengths += rs_length; _inc_cset_predicted_elapsed_time_ms += region_elapsed_time_ms; _inc_cset_bytes_used_before += used_bytes; // Cache the values we have added to the aggregated information // in the heap region in case we have to remove this region from // the incremental collection set, or it is updated by the // rset sampling code hr->set_recorded_rs_length(rs_length); hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms); } void G1CollectorPolicy::update_incremental_cset_info(HeapRegion* hr, size_t new_rs_length) { // Update the CSet information that is dependent on the new RS length assert(hr->is_young(), "Precondition"); assert(!SafepointSynchronize::is_at_safepoint(), "should not be at a safepoint"); // We could have updated _inc_cset_recorded_rs_lengths and // _inc_cset_predicted_elapsed_time_ms directly but we'd need to do // that atomically, as this code is executed by a concurrent // refinement thread, potentially concurrently with a mutator thread // allocating a new region and also updating the same fields. To // avoid the atomic operations we accumulate these updates on two // separate fields (*_diffs) and we'll just add them to the "main" // fields at the start of a GC. ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length(); ssize_t rs_lengths_diff = (ssize_t) new_rs_length - old_rs_length; _inc_cset_recorded_rs_lengths_diffs += rs_lengths_diff; double old_elapsed_time_ms = hr->predicted_elapsed_time_ms(); double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young()); double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms; _inc_cset_predicted_elapsed_time_ms_diffs += elapsed_ms_diff; hr->set_recorded_rs_length(new_rs_length); hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms); } void G1CollectorPolicy::add_region_to_incremental_cset_common(HeapRegion* hr) { assert(hr->is_young(), "invariant"); assert(hr->young_index_in_cset() > -1, "should have already been set"); assert(_inc_cset_build_state == Active, "Precondition"); // We need to clear and set the cached recorded/cached collection set // information in the heap region here (before the region gets added // to the collection set). An individual heap region's cached values // are calculated, aggregated with the policy collection set info, // and cached in the heap region here (initially) and (subsequently) // by the Young List sampling code. size_t rs_length = hr->rem_set()->occupied(); add_to_incremental_cset_info(hr, rs_length); assert(!hr->in_collection_set(), "invariant"); _g1->register_young_region_with_cset(hr); assert(hr->next_in_collection_set() == NULL, "invariant"); } // Add the region at the RHS of the incremental cset void G1CollectorPolicy::add_region_to_incremental_cset_rhs(HeapRegion* hr) { // We should only ever be appending survivors at the end of a pause assert(hr->is_survivor(), "Logic"); // Do the 'common' stuff add_region_to_incremental_cset_common(hr); // Now add the region at the right hand side if (_inc_cset_tail == NULL) { assert(_inc_cset_head == NULL, "invariant"); _inc_cset_head = hr; } else { _inc_cset_tail->set_next_in_collection_set(hr); } _inc_cset_tail = hr; } // Add the region to the LHS of the incremental cset void G1CollectorPolicy::add_region_to_incremental_cset_lhs(HeapRegion* hr) { // Survivors should be added to the RHS at the end of a pause assert(hr->is_eden(), "Logic"); // Do the 'common' stuff add_region_to_incremental_cset_common(hr); // Add the region at the left hand side hr->set_next_in_collection_set(_inc_cset_head); if (_inc_cset_head == NULL) { assert(_inc_cset_tail == NULL, "Invariant"); _inc_cset_tail = hr; } _inc_cset_head = hr; } #ifndef PRODUCT void G1CollectorPolicy::print_collection_set(HeapRegion* list_head, outputStream* st) { assert(list_head == inc_cset_head() || list_head == collection_set(), "must be"); st->print_cr("\nCollection_set:"); HeapRegion* csr = list_head; while (csr != NULL) { HeapRegion* next = csr->next_in_collection_set(); assert(csr->in_collection_set(), "bad CS"); st->print_cr(" " HR_FORMAT ", P: " PTR_FORMAT "N: " PTR_FORMAT ", age: %4d", HR_FORMAT_PARAMS(csr), p2i(csr->prev_top_at_mark_start()), p2i(csr->next_top_at_mark_start()), csr->age_in_surv_rate_group_cond()); csr = next; } } #endif // !PRODUCT double G1CollectorPolicy::reclaimable_bytes_perc(size_t reclaimable_bytes) const { // Returns the given amount of reclaimable bytes (that represents // the amount of reclaimable space still to be collected) as a // percentage of the current heap capacity. size_t capacity_bytes = _g1->capacity(); return (double) reclaimable_bytes * 100.0 / (double) capacity_bytes; } void G1CollectorPolicy::maybe_start_marking() { if (need_to_start_conc_mark("end of GC")) { // Note: this might have already been set, if during the last // pause we decided to start a cycle but at the beginning of // this pause we decided to postpone it. That's OK. collector_state()->set_initiate_conc_mark_if_possible(true); } } G1CollectorPolicy::PauseKind G1CollectorPolicy::young_gc_pause_kind() const { assert(!collector_state()->full_collection(), "must be"); if (collector_state()->during_initial_mark_pause()) { assert(collector_state()->last_gc_was_young(), "must be"); assert(!collector_state()->last_young_gc(), "must be"); return InitialMarkGC; } else if (collector_state()->last_young_gc()) { assert(!collector_state()->during_initial_mark_pause(), "must be"); assert(collector_state()->last_gc_was_young(), "must be"); return LastYoungGC; } else if (!collector_state()->last_gc_was_young()) { assert(!collector_state()->during_initial_mark_pause(), "must be"); assert(!collector_state()->last_young_gc(), "must be"); return MixedGC; } else { assert(collector_state()->last_gc_was_young(), "must be"); assert(!collector_state()->during_initial_mark_pause(), "must be"); assert(!collector_state()->last_young_gc(), "must be"); return YoungOnlyGC; } } void G1CollectorPolicy::record_pause(PauseKind kind, double start, double end) { // Manage the MMU tracker. For some reason it ignores Full GCs. if (kind != FullGC) { _mmu_tracker->add_pause(start, end); } // Manage the mutator time tracking from initial mark to first mixed gc. switch (kind) { case FullGC: abort_time_to_mixed_tracking(); break; case Cleanup: case Remark: case YoungOnlyGC: case LastYoungGC: _initial_mark_to_mixed.add_pause(end - start); break; case InitialMarkGC: _initial_mark_to_mixed.record_initial_mark_end(end); break; case MixedGC: _initial_mark_to_mixed.record_mixed_gc_start(start); break; default: ShouldNotReachHere(); } } void G1CollectorPolicy::abort_time_to_mixed_tracking() { _initial_mark_to_mixed.reset(); } bool G1CollectorPolicy::next_gc_should_be_mixed(const char* true_action_str, const char* false_action_str) const { if (cset_chooser()->is_empty()) { log_debug(gc, ergo)("%s (candidate old regions not available)", false_action_str); return false; } // Is the amount of uncollected reclaimable space above G1HeapWastePercent? size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes(); double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes); double threshold = (double) G1HeapWastePercent; if (reclaimable_perc <= threshold) { log_debug(gc, ergo)("%s (reclaimable percentage not over threshold). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, false_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent); return false; } log_debug(gc, ergo)("%s (candidate old regions available). candidate old regions: %u reclaimable: " SIZE_FORMAT " (%1.2f) threshold: " UINTX_FORMAT, true_action_str, cset_chooser()->remaining_regions(), reclaimable_bytes, reclaimable_perc, G1HeapWastePercent); return true; } uint G1CollectorPolicy::calc_min_old_cset_length() const { // The min old CSet region bound is based on the maximum desired // number of mixed GCs after a cycle. I.e., even if some old regions // look expensive, we should add them to the CSet anyway to make // sure we go through the available old regions in no more than the // maximum desired number of mixed GCs. // // The calculation is based on the number of marked regions we added // to the CSet chooser in the first place, not how many remain, so // that the result is the same during all mixed GCs that follow a cycle. const size_t region_num = (size_t) cset_chooser()->length(); const size_t gc_num = (size_t) MAX2(G1MixedGCCountTarget, (uintx) 1); size_t result = region_num / gc_num; // emulate ceiling if (result * gc_num < region_num) { result += 1; } return (uint) result; } uint G1CollectorPolicy::calc_max_old_cset_length() const { // The max old CSet region bound is based on the threshold expressed // as a percentage of the heap size. I.e., it should bound the // number of old regions added to the CSet irrespective of how many // of them are available. const G1CollectedHeap* g1h = G1CollectedHeap::heap(); const size_t region_num = g1h->num_regions(); const size_t perc = (size_t) G1OldCSetRegionThresholdPercent; size_t result = region_num * perc / 100; // emulate ceiling if (100 * result < region_num * perc) { result += 1; } return (uint) result; } double G1CollectorPolicy::finalize_young_cset_part(double target_pause_time_ms) { double young_start_time_sec = os::elapsedTime(); YoungList* young_list = _g1->young_list(); finalize_incremental_cset_building(); guarantee(target_pause_time_ms > 0.0, "target_pause_time_ms = %1.6lf should be positive", target_pause_time_ms); guarantee(_collection_set == NULL, "Precondition"); double base_time_ms = predict_base_elapsed_time_ms(_pending_cards); double time_remaining_ms = MAX2(target_pause_time_ms - base_time_ms, 0.0); log_trace(gc, ergo, cset)("Start choosing CSet. pending cards: " SIZE_FORMAT " predicted base time: %1.2fms remaining time: %1.2fms target pause time: %1.2fms", _pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms); collector_state()->set_last_gc_was_young(collector_state()->gcs_are_young()); // The young list is laid with the survivor regions from the previous // pause are appended to the RHS of the young list, i.e. // [Newly Young Regions ++ Survivors from last pause]. uint survivor_region_length = young_list->survivor_length(); uint eden_region_length = young_list->eden_length(); init_cset_region_lengths(eden_region_length, survivor_region_length); HeapRegion* hr = young_list->first_survivor_region(); while (hr != NULL) { assert(hr->is_survivor(), "badly formed young list"); // There is a convention that all the young regions in the CSet // are tagged as "eden", so we do this for the survivors here. We // use the special set_eden_pre_gc() as it doesn't check that the // region is free (which is not the case here). hr->set_eden_pre_gc(); hr = hr->get_next_young_region(); } // Clear the fields that point to the survivor list - they are all young now. young_list->clear_survivors(); _collection_set = _inc_cset_head; _collection_set_bytes_used_before = _inc_cset_bytes_used_before; time_remaining_ms = MAX2(time_remaining_ms - _inc_cset_predicted_elapsed_time_ms, 0.0); log_trace(gc, ergo, cset)("Add young regions to CSet. eden: %u regions, survivors: %u regions, predicted young region time: %1.2fms, target pause time: %1.2fms", eden_region_length, survivor_region_length, _inc_cset_predicted_elapsed_time_ms, target_pause_time_ms); // The number of recorded young regions is the incremental // collection set's current size set_recorded_rs_lengths(_inc_cset_recorded_rs_lengths); double young_end_time_sec = os::elapsedTime(); phase_times()->record_young_cset_choice_time_ms((young_end_time_sec - young_start_time_sec) * 1000.0); return time_remaining_ms; } void G1CollectorPolicy::finalize_old_cset_part(double time_remaining_ms) { double non_young_start_time_sec = os::elapsedTime(); double predicted_old_time_ms = 0.0; if (!collector_state()->gcs_are_young()) { cset_chooser()->verify(); const uint min_old_cset_length = calc_min_old_cset_length(); const uint max_old_cset_length = calc_max_old_cset_length(); uint expensive_region_num = 0; bool check_time_remaining = adaptive_young_list_length(); HeapRegion* hr = cset_chooser()->peek(); while (hr != NULL) { if (old_cset_region_length() >= max_old_cset_length) { // Added maximum number of old regions to the CSet. log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached max). old %u regions, max %u regions", old_cset_region_length(), max_old_cset_length); break; } // Stop adding regions if the remaining reclaimable space is // not above G1HeapWastePercent. size_t reclaimable_bytes = cset_chooser()->remaining_reclaimable_bytes(); double reclaimable_perc = reclaimable_bytes_perc(reclaimable_bytes); double threshold = (double) G1HeapWastePercent; if (reclaimable_perc <= threshold) { // We've added enough old regions that the amount of uncollected // reclaimable space is at or below the waste threshold. Stop // adding old regions to the CSet. log_debug(gc, ergo, cset)("Finish adding old regions to CSet (reclaimable percentage not over threshold). " "old %u regions, max %u regions, reclaimable: " SIZE_FORMAT "B (%1.2f%%) threshold: " UINTX_FORMAT "%%", old_cset_region_length(), max_old_cset_length, reclaimable_bytes, reclaimable_perc, G1HeapWastePercent); break; } double predicted_time_ms = predict_region_elapsed_time_ms(hr, collector_state()->gcs_are_young()); if (check_time_remaining) { if (predicted_time_ms > time_remaining_ms) { // Too expensive for the current CSet. if (old_cset_region_length() >= min_old_cset_length) { // We have added the minimum number of old regions to the CSet, // we are done with this CSet. log_debug(gc, ergo, cset)("Finish adding old regions to CSet (predicted time is too high). " "predicted time: %1.2fms, remaining time: %1.2fms old %u regions, min %u regions", predicted_time_ms, time_remaining_ms, old_cset_region_length(), min_old_cset_length); break; } // We'll add it anyway given that we haven't reached the // minimum number of old regions. expensive_region_num += 1; } } else { if (old_cset_region_length() >= min_old_cset_length) { // In the non-auto-tuning case, we'll finish adding regions // to the CSet if we reach the minimum. log_debug(gc, ergo, cset)("Finish adding old regions to CSet (old CSet region num reached min). old %u regions, min %u regions", old_cset_region_length(), min_old_cset_length); break; } } // We will add this region to the CSet. time_remaining_ms = MAX2(time_remaining_ms - predicted_time_ms, 0.0); predicted_old_time_ms += predicted_time_ms; cset_chooser()->pop(); // already have region via peek() _g1->old_set_remove(hr); add_old_region_to_cset(hr); hr = cset_chooser()->peek(); } if (hr == NULL) { log_debug(gc, ergo, cset)("Finish adding old regions to CSet (candidate old regions not available)"); } if (expensive_region_num > 0) { // We print the information once here at the end, predicated on // whether we added any apparently expensive regions or not, to // avoid generating output per region. log_debug(gc, ergo, cset)("Added expensive regions to CSet (old CSet region num not reached min)." "old: %u regions, expensive: %u regions, min: %u regions, remaining time: %1.2fms", old_cset_region_length(), expensive_region_num, min_old_cset_length, time_remaining_ms); } cset_chooser()->verify(); } stop_incremental_cset_building(); log_debug(gc, ergo, cset)("Finish choosing CSet. old: %u regions, predicted old region time: %1.2fms, time remaining: %1.2f", old_cset_region_length(), predicted_old_time_ms, time_remaining_ms); double non_young_end_time_sec = os::elapsedTime(); phase_times()->record_non_young_cset_choice_time_ms((non_young_end_time_sec - non_young_start_time_sec) * 1000.0); }