|
/*
* Copyright (c) 2016, 2022, 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.
*
*/
#ifndef SHARE_GC_G1_G1POLICY_HPP
#define SHARE_GC_G1_G1POLICY_HPP
#include "gc/g1/g1CollectorState.hpp"
#include "gc/g1/g1ConcurrentStartToMixedTimeTracker.hpp"
#include "gc/g1/g1GCPhaseTimes.hpp"
#include "gc/g1/g1HeapRegionAttr.hpp"
#include "gc/g1/g1MMUTracker.hpp"
#include "gc/g1/g1OldGenAllocationTracker.hpp"
#include "gc/g1/g1RemSetTrackingPolicy.hpp"
#include "gc/g1/g1Predictions.hpp"
#include "gc/g1/g1YoungGenSizer.hpp"
#include "gc/shared/gcCause.hpp"
#include "runtime/atomic.hpp"
#include "utilities/pair.hpp"
#include "utilities/ticks.hpp"
// A G1Policy makes policy decisions that determine the
// characteristics of the collector. Examples include:
// * choice of collection set.
// * when to collect.
class HeapRegion;
class G1CollectionSet;
class G1CollectionSetCandidates;
class G1CollectionSetChooser;
class G1IHOPControl;
class G1Analytics;
class G1SurvivorRegions;
class GCPolicyCounters;
class STWGCTimer;
class G1Policy: public CHeapObj<mtGC> {
private:
static G1IHOPControl* create_ihop_control(const G1OldGenAllocationTracker* old_gen_alloc_tracker,
const G1Predictions* predictor);
// Update the IHOP control with necessary statistics.
void update_ihop_prediction(double mutator_time_s,
bool this_gc_was_young_only);
void report_ihop_statistics();
G1Predictions _predictor;
G1Analytics* _analytics;
G1RemSetTrackingPolicy _remset_tracker;
G1MMUTracker* _mmu_tracker;
// Tracking the allocation in the old generation between
// two GCs.
G1OldGenAllocationTracker _old_gen_alloc_tracker;
G1IHOPControl* _ihop_control;
GCPolicyCounters* _policy_counters;
double _full_collection_start_sec;
// Desired young gen length without taking actually available free regions into
// account.
volatile uint _young_list_desired_length;
// Actual target length given available free memory.
volatile uint _young_list_target_length;
// The max number of regions we can extend the eden by while the GC
// locker is active. This should be >= _young_list_target_length;
volatile uint _young_list_max_length;
// The survivor rate groups below must be initialized after the predictor because they
// indirectly use it through the "this" object passed to their constructor.
G1SurvRateGroup* _eden_surv_rate_group;
G1SurvRateGroup* _survivor_surv_rate_group;
double _reserve_factor;
// This will be set when the heap is expanded
// for the first time during initialization.
uint _reserve_regions;
G1YoungGenSizer _young_gen_sizer;
uint _free_regions_at_end_of_collection;
// These values are predictions of how much we think will survive in each
// section of the heap.
size_t _predicted_surviving_bytes_from_survivor;
size_t _predicted_surviving_bytes_from_old;
size_t _rs_length;
size_t _pending_cards_at_gc_start;
G1ConcurrentStartToMixedTimeTracker _concurrent_start_to_mixed;
bool should_update_surv_rate_group_predictors() {
return collector_state()->in_young_only_phase() && !collector_state()->mark_or_rebuild_in_progress();
}
double logged_cards_processing_time() const;
public:
const G1Predictions& predictor() const { return _predictor; }
const G1Analytics* analytics() const { return const_cast<const G1Analytics*>(_analytics); }
G1RemSetTrackingPolicy* remset_tracker() { return &_remset_tracker; }
G1OldGenAllocationTracker* old_gen_alloc_tracker() { return &_old_gen_alloc_tracker; }
void set_region_eden(HeapRegion* hr) {
hr->set_eden();
hr->install_surv_rate_group(_eden_surv_rate_group);
}
void set_region_survivor(HeapRegion* hr) {
assert(hr->is_survivor(), "pre-condition");
hr->install_surv_rate_group(_survivor_surv_rate_group);
}
void record_rs_length(size_t rs_length) {
_rs_length = rs_length;
}
double predict_base_time_ms(size_t pending_cards) const;
private:
// Base time contains handling remembered sets and constant other time of the
// whole young gen, refinement buffers, and copying survivors.
// Basically everything but copying eden regions.
double predict_base_time_ms(size_t pending_cards, size_t rs_length) const;
// Copy time for a region is copying live data.
double predict_region_copy_time_ms(HeapRegion* hr) const;
// Merge-scan time for a region is handling remembered sets of that region (as a single unit).
double predict_region_merge_scan_time(HeapRegion* hr, bool for_young_only_phase) const;
// Non-copy time for a region is handling remembered sets and other time.
double predict_region_non_copy_time_ms(HeapRegion* hr, bool for_young_only_phase) const;
public:
// Predict other time for count young regions.
double predict_young_region_other_time_ms(uint count) const;
// Predict copying live data time for count eden regions. Return the predict bytes if
// bytes_to_copy is non-nullptr.
double predict_eden_copy_time_ms(uint count, size_t* bytes_to_copy = nullptr) const;
// Total time for a region is handling remembered sets (as a single unit), copying its live data
// and other time.
double predict_region_total_time_ms(HeapRegion* hr, bool for_young_only_phase) const;
void cset_regions_freed() {
bool update = should_update_surv_rate_group_predictors();
_eden_surv_rate_group->all_surviving_words_recorded(predictor(), update);
_survivor_surv_rate_group->all_surviving_words_recorded(predictor(), update);
}
G1MMUTracker* mmu_tracker() {
return _mmu_tracker;
}
const G1MMUTracker* mmu_tracker() const {
return _mmu_tracker;
}
double max_pause_time_ms() const {
return _mmu_tracker->max_gc_time() * 1000.0;
}
private:
G1CollectionSet* _collection_set;
double average_time_ms(G1GCPhaseTimes::GCParPhases phase) const;
double other_time_ms(double pause_time_ms) const;
double young_other_time_ms() const;
double non_young_other_time_ms() const;
double constant_other_time_ms(double pause_time_ms) const;
G1CollectionSetChooser* cset_chooser() const;
// Stash a pointer to the g1 heap.
G1CollectedHeap* _g1h;
STWGCTimer* _phase_times_timer;
// Lazily initialized
mutable G1GCPhaseTimes* _phase_times;
// This set of variables tracks the collector efficiency, in order to
// determine whether we should initiate a new marking.
double _mark_remark_start_sec;
double _mark_cleanup_start_sec;
// Updates the internal young gen maximum and target and desired lengths.
// If no parameters are passed, predict pending cards and the RS length using
// the prediction model.
void update_young_length_bounds();
void update_young_length_bounds(size_t pending_cards, size_t rs_length);
// Calculate and return the minimum desired eden length based on the MMU target.
uint calculate_desired_eden_length_by_mmu() const;
// Calculate the desired eden length meeting the pause time goal.
// The parameters are: rs_length represents the prediction of how large the
// young RSet lengths will be, min_eden_length and max_eden_length are the bounds
// (inclusive) within eden can grow.
uint calculate_desired_eden_length_by_pause(double base_time_ms,
uint min_eden_length,
uint max_eden_length) const;
// Calculate the desired eden length that can fit into the pause time
// goal before young only gcs.
uint calculate_desired_eden_length_before_young_only(double base_time_ms,
uint min_eden_length,
uint max_eden_length) const;
// Calculates the desired eden length before mixed gc so that after adding the
// minimum amount of old gen regions from the collection set, the eden fits into
// the pause time goal.
uint calculate_desired_eden_length_before_mixed(double base_time_ms,
uint min_eden_length,
uint max_eden_length) const;
// Calculate desired young length based on current situation without taking actually
// available free regions into account.
uint calculate_young_desired_length(size_t pending_cards, size_t rs_length) const;
// Limit the given desired young length to available free regions.
uint calculate_young_target_length(uint desired_young_length) const;
// The GCLocker might cause us to need more regions than the target. Calculate
// the maximum number of regions to use in that case.
uint calculate_young_max_length(uint target_young_length) const;
size_t predict_bytes_to_copy(HeapRegion* hr) const;
double predict_survivor_regions_evac_time() const;
// Check whether a given young length (young_length) fits into the
// given target pause time and whether the prediction for the amount
// of objects to be copied for the given length will fit into the
// given free space (expressed by base_free_regions). It is used by
// calculate_young_list_target_length().
bool predict_will_fit(uint young_length, double base_time_ms,
uint base_free_regions, double target_pause_time_ms) const;
public:
size_t pending_cards_at_gc_start() const { return _pending_cards_at_gc_start; }
// Calculate the minimum number of old regions we'll add to the CSet
// during a mixed GC.
uint calc_min_old_cset_length(G1CollectionSetCandidates* candidates) const;
// Calculate the maximum number of old regions we'll add to the CSet
// during a mixed GC.
uint calc_max_old_cset_length() 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.
double reclaimable_bytes_percent(size_t reclaimable_bytes) const;
private:
void clear_collection_set_candidates();
// Sets up marking if proper conditions are met.
void maybe_start_marking();
// Manage time-to-mixed tracking.
void update_time_to_mixed_tracking(G1GCPauseType gc_type, double start, double end);
// Record the given STW pause with the given start and end times (in s).
void record_pause(G1GCPauseType gc_type,
double start,
double end,
bool evacuation_failure = false);
void update_gc_pause_time_ratios(G1GCPauseType gc_type, double start_sec, double end_sec);
// Indicate that we aborted marking before doing any mixed GCs.
void abort_time_to_mixed_tracking();
public:
G1Policy(STWGCTimer* gc_timer);
virtual ~G1Policy();
G1CollectorState* collector_state() const;
G1GCPhaseTimes* phase_times() const;
// Check the current value of the young list RSet length and
// compare it against the last prediction. If the current value is
// higher, recalculate the young list target length prediction.
void revise_young_list_target_length(size_t rs_length);
// This should be called after the heap is resized.
void record_new_heap_size(uint new_number_of_regions);
void init(G1CollectedHeap* g1h, G1CollectionSet* collection_set);
// Record the start and end of the young gc pause.
void record_young_gc_pause_start();
void record_young_gc_pause_end(bool evacuation_failed);
bool need_to_start_conc_mark(const char* source, size_t alloc_word_size = 0);
bool concurrent_operation_is_full_mark(const char* msg = NULL);
bool about_to_start_mixed_phase() const;
// Record the start and end of the actual collection part of the evacuation pause.
void record_young_collection_start();
void record_young_collection_end(bool concurrent_operation_is_full_mark, bool evacuation_failure);
// Record the start and end of a full collection.
void record_full_collection_start();
void record_full_collection_end();
// Must currently be called while the world is stopped.
void record_concurrent_mark_init_end();
// Record start and end of remark.
void record_concurrent_mark_remark_start();
void record_concurrent_mark_remark_end();
// Record start, end, and completion of cleanup.
void record_concurrent_mark_cleanup_start();
void record_concurrent_mark_cleanup_end(bool has_rebuilt_remembered_sets);
bool next_gc_should_be_mixed(const char* no_candidates_str) const;
// Amount of allowed waste in bytes in the collection set.
size_t allowed_waste_in_collection_set() const;
// Calculate and return the number of initial and optional old gen regions from
// the given collection set candidates and the remaining time.
void calculate_old_collection_set_regions(G1CollectionSetCandidates* candidates,
double time_remaining_ms,
uint& num_initial_regions,
uint& num_optional_regions);
// Calculate the number of optional regions from the given collection set candidates,
// the remaining time and the maximum number of these regions and return the number
// of actually selected regions in num_optional_regions.
void calculate_optional_collection_set_regions(G1CollectionSetCandidates* candidates,
uint const max_optional_regions,
double time_remaining_ms,
uint& num_optional_regions);
// Returns whether a collection should be done proactively, taking into
// account the current number of free regions and the expected survival
// rates in each section of the heap.
bool preventive_collection_required(uint region_count);
private:
// Predict the number of bytes of surviving objects from survivor and old
// regions and update the associated members.
void update_survival_estimates_for_next_collection();
// Set the state to start a concurrent marking cycle and clear
// _initiate_conc_mark_if_possible because it has now been
// acted on.
void initiate_conc_mark();
public:
// This sets the initiate_conc_mark_if_possible() flag to start a
// new cycle, as long as we are not already in one. It's best if it
// is called during a safepoint when the test whether a cycle is in
// progress or not is stable.
bool force_concurrent_start_if_outside_cycle(GCCause::Cause gc_cause);
// Decide whether this garbage collection pause should be a concurrent start
// pause and update the collector state accordingly.
// We decide on a concurrent start pause if initiate_conc_mark_if_possible() is
// true, the concurrent marking thread has completed its work for the previous
// cycle, and we are not shutting down the VM.
// This must be called at the very beginning of an evacuation pause.
void decide_on_concurrent_start_pause();
uint young_list_desired_length() const { return Atomic::load(&_young_list_desired_length); }
uint young_list_target_length() const { return Atomic::load(&_young_list_target_length); }
uint young_list_max_length() const { return Atomic::load(&_young_list_max_length); }
bool should_allocate_mutator_region() const;
bool can_expand_young_list() const;
bool use_adaptive_young_list_length() const;
// Return an estimate of the number of bytes used in young gen.
// precondition: holding Heap_lock
size_t estimate_used_young_bytes_locked() const;
void transfer_survivors_to_cset(const G1SurvivorRegions* survivors);
// Record and log stats and pending cards before not-full collection.
// thread_buffer_cards is the number of cards that were in per-thread
// buffers. pending_cards includes thread_buffer_cards.
void record_concurrent_refinement_stats(size_t pending_cards,
size_t thread_buffer_cards);
private:
//
// Survivor regions policy.
//
// Current tenuring threshold, set to 0 if the collector reaches the
// maximum amount of survivors regions.
uint _tenuring_threshold;
// The limit on the number of regions allocated for survivors.
uint _max_survivor_regions;
AgeTable _survivors_age_table;
size_t desired_survivor_size(uint max_regions) const;
// Fraction used when predicting how many optional regions to include in
// the CSet. This fraction of the available time is used for optional regions,
// the rest is used to add old regions to the normal CSet.
double optional_prediction_fraction() { return 0.2; }
public:
// Fraction used when evacuating the optional regions. This fraction of the
// remaining time is used to choose what regions to include in the evacuation.
double optional_evacuation_fraction() { return 0.75; }
uint tenuring_threshold() const { return _tenuring_threshold; }
uint max_survivor_regions() {
return _max_survivor_regions;
}
void start_adding_survivor_regions() {
_survivor_surv_rate_group->start_adding_regions();
}
void stop_adding_survivor_regions() {
_survivor_surv_rate_group->stop_adding_regions();
}
void record_age_table(AgeTable* age_table) {
_survivors_age_table.merge(age_table);
}
void print_age_table();
void update_survivors_policy();
};
#endif // SHARE_GC_G1_G1POLICY_HPP
¤ Dauer der Verarbeitung: 0.18 Sekunden
(vorverarbeitet)
¤
|
Haftungshinweis
Die Informationen auf dieser Webseite wurden
nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit,
noch Qualität der bereit gestellten Informationen zugesichert.
Bemerkung:
Die farbliche Syntaxdarstellung ist noch experimentell.
|
