/* * 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/g1Analytics.hpp" #include "gc/g1/g1CollectedHeap.inline.hpp" #include "gc/g1/g1CollectionSet.hpp" #include "gc/g1/g1CollectorPolicy.hpp" #include "gc/g1/g1ConcurrentMark.hpp" #include "gc/g1/g1IHOPControl.hpp" #include "gc/g1/g1GCPhaseTimes.hpp" #include "gc/g1/g1YoungGenSizer.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" G1CollectorPolicy::G1CollectorPolicy() : _predictor(G1ConfidencePercent / 100.0), _analytics(new G1Analytics(&_predictor)), _pause_time_target_ms((double) MaxGCPauseMillis), _rs_lengths_prediction(0), _max_survivor_regions(0), _survivors_age_table(true), _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(); _phase_times = new G1GCPhaseTimes(ParallelGCThreads); // 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. guarantee(MaxGCPauseMillis >= 1, "Range checking for MaxGCPauseMillis should guarantee that value is >= 1"); // 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); } guarantee(GCPauseIntervalMillis >= 1, "Constraint for GCPauseIntervalMillis should guarantee that value is >= 1"); guarantee(GCPauseIntervalMillis > MaxGCPauseMillis, "Constraint for GCPauseIntervalMillis should guarantee that GCPauseIntervalMillis > MaxGCPauseMillis"); double max_gc_time = (double) MaxGCPauseMillis / 1000.0; double time_slice = (double) GCPauseIntervalMillis / 1000.0; _mmu_tracker = new G1MMUTrackerQueue(time_slice, max_gc_time); _tenuring_threshold = MaxTenuringThreshold; guarantee(G1ReservePercent <= 50, "Range checking should not allow values over 50."); _reserve_factor = (double) G1ReservePercent / 100.0; // This will be set when the heap is expanded // for the first time during initialization. _reserve_regions = 0; _ihop_control = create_ihop_control(); } G1CollectorPolicy::~G1CollectorPolicy() { delete _ihop_control; } 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(); } 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); } } void G1CollectorPolicy::initialize_flags() { if (G1HeapRegionSize != HeapRegion::GrainBytes) { FLAG_SET_ERGO(size_t, G1HeapRegionSize, HeapRegion::GrainBytes); } guarantee(SurvivorRatio >= 1, "Range checking for SurvivorRatio should guarantee that value is >= 1"); 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(); _collection_set = _g1->collection_set(); _collection_set->set_policy(this); 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 _collection_set->start_incremental_building(); } void G1CollectorPolicy::note_gc_start() { phase_times()->note_gc_start(); } // 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 = _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->during_concurrent_mark()); double young_other_time_ms = _analytics->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. size_t expected_bytes_to_copy = (size_t)(bytes_to_copy * safety_factor()); 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); _ihop_control->update_target_occupancy(new_number_of_regions * HeapRegion::GrainBytes); } uint G1CollectorPolicy::calculate_young_list_desired_min_length( uint base_min_length) const { uint desired_min_length = 0; if (adaptive_young_list_length()) { if (_analytics->num_alloc_rate_ms() > 3) { double now_sec = os::elapsedTime(); double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0; double alloc_rate_ms = _analytics->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(_analytics->predict_rs_lengths()); } 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). const uint base_min_length = _g1->young_list()->survivor_length(); 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 > base_min_length, "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 = _analytics->predict_pending_cards(); size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff(); size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, /* gcs_are_young */ true); 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 = _g1->young_list()->first_survivor_region(); r != NULL && r != _g1->young_list()->last_survivor_region()->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(size_t rs_lengths) { guarantee( adaptive_young_list_length(), "should not call this otherwise" ); 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(_analytics->predict_rs_lengths()); } 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; _analytics->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 _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->reset_bytes_used_before(); _collection_set->reset_bytes_live_before(); _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; _analytics->report_concurrent_mark_remark_times_ms(elapsed_time_ms); _analytics->append_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(); } CollectionSetChooser* G1CollectorPolicy::cset_chooser() const { return _collection_set->cset_chooser(); } 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 - _analytics->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 = _collection_set->eden_region_length(); double alloc_rate_ms = (double) regions_allocated / app_time_ms; _analytics->report_alloc_rate_ms(alloc_rate_ms); double interval_ms = (end_time_sec - _analytics->last_known_gc_end_time_sec()) * 1000.0; _analytics->update_recent_gc_times(end_time_sec, pause_time_ms); _analytics->compute_pause_time_ratio(interval_ms, pause_time_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; _analytics->report_cost_per_card_ms(cost_per_card_ms); } _analytics->report_cost_scan_hcc(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; _analytics->report_cost_per_entry_ms(cost_per_entry_ms, collector_state()->last_gc_was_young()); } if (_max_rs_lengths > 0) { double cards_per_entry_ratio = (double) cards_scanned / (double) _max_rs_lengths; _analytics->report_cards_per_entry_ratio(cards_per_entry_ratio, collector_state()->last_gc_was_young()); } // 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; size_t recorded_rs_lengths = _collection_set->recorded_rs_lengths(); if (_max_rs_lengths > recorded_rs_lengths) { rs_length_diff = _max_rs_lengths - recorded_rs_lengths; } _analytics->report_rs_length_diff((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; _analytics->report_cost_per_byte_ms(cost_per_byte_ms, collector_state()->in_marking_window()); } if (_collection_set->young_region_length() > 0) { _analytics->report_young_other_cost_per_region_ms(young_other_time_ms() / _collection_set->young_region_length()); } if (_collection_set->old_region_length() > 0) { _analytics->report_non_young_other_cost_per_region_ms(non_young_other_time_ms() / _collection_set->old_region_length()); } _analytics->report_constant_other_time_ms(constant_other_time_ms(pause_time_ms)); _analytics->report_pending_cards((double) _pending_cards); _analytics->report_rs_lengths((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; } _g1->concurrent_g1_refine()->adjust(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, &_predictor, G1ReservePercent, G1HeapWastePercent); } else { return new G1StaticIHOPControl(InitiatingHeapOccupancyPercent); } } 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(); } 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 = _predictor.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 _analytics->predict_rs_update_time_ms(pending_cards) + _analytics->predict_rs_scan_time_ms(scanned_cards, collector_state()->gcs_are_young()) + _analytics->predict_constant_other_time_ms(); } double G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards) const { size_t rs_length = _analytics->predict_rs_lengths() + _analytics->predict_rs_length_diff(); size_t card_num = _analytics->predict_card_num(rs_length, collector_state()->gcs_are_young()); 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(); // Predicting the number of cards is based on which type of GC // we're predicting for. size_t card_num = _analytics->predict_card_num(rs_length, for_young_gc); size_t bytes_to_copy = predict_bytes_to_copy(hr); double region_elapsed_time_ms = _analytics->predict_rs_scan_time_ms(card_num, collector_state()->gcs_are_young()) + _analytics->predict_object_copy_time_ms(bytes_to_copy, collector_state()->during_concurrent_mark()); // 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 += _analytics->predict_young_other_time_ms(1); } else { region_elapsed_time_ms += _analytics->predict_non_young_other_time_ms(1); } return region_elapsed_time_ms; } 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)"); } } } void G1CollectorPolicy::record_concurrent_mark_cleanup_end() { cset_chooser()->rebuild(_g1->workers(), _g1->num_regions()); double end_sec = os::elapsedTime(); double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0; _analytics->report_concurrent_mark_cleanup_times_ms(elapsed_time_ms); _analytics->append_prev_collection_pause_end_ms(elapsed_time_ms); record_pause(Cleanup, _mark_cleanup_start_sec, end_sec); } 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; } size_t G1CollectorPolicy::available_bytes_estimate() { size_t estimated_available_bytes = 0; if (_free_regions_at_end_of_collection > _reserve_regions) { uint available_regions = _free_regions_at_end_of_collection - _reserve_regions; estimated_available_bytes = (size_t)((available_regions * HeapRegion::GrainBytes) / safety_factor()); } return estimated_available_bytes; } void G1CollectorPolicy::finalize_collection_set(double target_pause_time_ms) { double time_remaining_ms = _collection_set->finalize_young_part(target_pause_time_ms); _collection_set->finalize_old_part(time_remaining_ms); }