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/*
* Copyright (c) 2015, 2020, 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_G1IHOPCONTROL_HPP
#define SHARE_GC_G1_G1IHOPCONTROL_HPP
#include "gc/g1/g1OldGenAllocationTracker.hpp"
#include "memory/allocation.hpp"
#include "utilities/numberSeq.hpp"
class G1Predictions;
class G1NewTracer;
// Base class for algorithms that calculate the heap occupancy at which
// concurrent marking should start. This heap usage threshold should be relative
// to old gen size.
class G1IHOPControl : public CHeapObj<mtGC> {
protected:
// The initial IHOP value relative to the target occupancy.
double _initial_ihop_percent;
// The target maximum occupancy of the heap. The target occupancy is the number
// of bytes when marking should be finished and reclaim started.
size_t _target_occupancy;
// Most recent complete mutator allocation period in seconds.
double _last_allocation_time_s;
const G1OldGenAllocationTracker* _old_gen_alloc_tracker;
// Initialize an instance with the old gen allocation tracker and the
// initial IHOP value in percent. The target occupancy will be updated
// at the first heap expansion.
G1IHOPControl(double ihop_percent, G1OldGenAllocationTracker const* old_gen_alloc_tracker);
// Most recent time from the end of the concurrent start to the start of the first
// mixed gc.
virtual double last_marking_length_s() const = 0;
public:
virtual ~G1IHOPControl() { }
// Get the current non-young occupancy at which concurrent marking should start.
virtual size_t get_conc_mark_start_threshold() = 0;
// Adjust target occupancy.
virtual void update_target_occupancy(size_t new_target_occupancy);
// Update information about time during which allocations in the Java heap occurred,
// how large these allocations were in bytes, and an additional buffer.
// The allocations should contain any amount of space made unusable for further
// allocation, e.g. any waste caused by TLAB allocation, space at the end of
// humongous objects that can not be used for allocation, etc.
// Together with the target occupancy, this additional buffer should contain the
// difference between old gen size and total heap size at the start of reclamation,
// and space required for that reclamation.
virtual void update_allocation_info(double allocation_time_s, size_t additional_buffer_size);
// Update the time spent in the mutator beginning from the end of concurrent start to
// the first mixed gc.
virtual void update_marking_length(double marking_length_s) = 0;
virtual void print();
virtual void send_trace_event(G1NewTracer* tracer);
};
// The returned concurrent mark starting occupancy threshold is a fixed value
// relative to the maximum heap size.
class G1StaticIHOPControl : public G1IHOPControl {
// Most recent mutator time between the end of concurrent mark to the start of the
// first mixed gc.
double _last_marking_length_s;
protected:
double last_marking_length_s() const { return _last_marking_length_s; }
public:
G1StaticIHOPControl(double ihop_percent, G1OldGenAllocationTracker const* old_gen_alloc_tracker);
size_t get_conc_mark_start_threshold() {
guarantee(_target_occupancy > 0, "Target occupancy must have been initialized.");
return (size_t) (_initial_ihop_percent * _target_occupancy / 100.0);
}
virtual void update_marking_length(double marking_length_s) {
assert(marking_length_s > 0.0, "Marking length must be larger than zero but is %.3f", marking_length_s);
_last_marking_length_s = marking_length_s;
}
};
// This algorithm tries to return a concurrent mark starting occupancy value that
// makes sure that during marking the given target occupancy is never exceeded,
// based on predictions of current allocation rate and time periods between
// concurrent start and the first mixed gc.
class G1AdaptiveIHOPControl : public G1IHOPControl {
size_t _heap_reserve_percent; // Percentage of maximum heap capacity we should avoid to touch
size_t _heap_waste_percent; // Percentage of free heap that should be considered as waste.
const G1Predictions * _predictor;
TruncatedSeq _marking_times_s;
TruncatedSeq _allocation_rate_s;
// The most recent unrestrained size of the young gen. This is used as an additional
// factor in the calculation of the threshold, as the threshold is based on
// non-young gen occupancy at the end of GC. For the IHOP threshold, we need to
// consider the young gen size during that time too.
// Since we cannot know what young gen sizes are used in the future, we will just
// use the current one. We expect that this one will be one with a fairly large size,
// as there is no marking or mixed gc that could impact its size too much.
size_t _last_unrestrained_young_size;
// Get a new prediction bounded below by zero from the given sequence.
double predict(TruncatedSeq const* seq) const;
bool have_enough_data_for_prediction() const;
// The "actual" target threshold the algorithm wants to keep during and at the
// end of marking. This is typically lower than the requested threshold, as the
// algorithm needs to consider restrictions by the environment.
size_t actual_target_threshold() const;
// This method calculates the old gen allocation rate based on the net survived
// bytes that are allocated in the old generation in the last mutator period.
double last_mutator_period_old_allocation_rate() const;
protected:
virtual double last_marking_length_s() const { return _marking_times_s.last(); }
public:
G1AdaptiveIHOPControl(double ihop_percent,
G1OldGenAllocationTracker const* old_gen_alloc_tracker,
G1Predictions const* predictor,
size_t heap_reserve_percent, // The percentage of total heap capacity that should not be tapped into.
size_t heap_waste_percent); // The percentage of the free space in the heap that we think is not usable for allocation.
virtual size_t get_conc_mark_start_threshold();
virtual void update_allocation_info(double allocation_time_s, size_t additional_buffer_size);
virtual void update_marking_length(double marking_length_s);
virtual void print();
virtual void send_trace_event(G1NewTracer* tracer);
};
#endif // SHARE_GC_G1_G1IHOPCONTROL_HPP
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