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* QEMU throttling infrastructure
* Copyright (C) Nodalink, SARL. 2013
* Author:
* BenoƮt Canet <>
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation; either version 2 or
* (at your option) version 3 of the License.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <>.
#ifndef THROTTLE_H
#define THROTTLE_H
#include <stdint.h>
#include "qemu-common.h"
#include "qemu/timer.h"
#define NANOSECONDS_PER_SECOND 1000000000.0
typedef enum {
} BucketType;
* The max parameter of the leaky bucket throttling algorithm can be used to
* allow the guest to do bursts.
* The max value is a pool of I/O that the guest can use without being throttled
* at all. Throttling is triggered once this pool is empty.
typedef struct LeakyBucket {
double avg; /* average goal in units per second */
double max; /* leaky bucket max burst in units */
double level; /* bucket level in units */
} LeakyBucket;
/* The following structure is used to configure a ThrottleState
* It contains a bit of state: the bucket field of the LeakyBucket structure.
* However it allows to keep the code clean and the bucket field is reset to
* zero at the right time.
typedef struct ThrottleConfig {
LeakyBucket buckets[BUCKETS_COUNT]; /* leaky buckets */
uint64_t op_size; /* size of an operation in bytes */
} ThrottleConfig;
typedef struct ThrottleState {
ThrottleConfig cfg; /* configuration */
int64_t previous_leak; /* timestamp of the last leak done */
QEMUTimer * timers[2]; /* timers used to do the throttling */
QEMUClockType clock_type; /* the clock used */
} ThrottleState;
/* operations on single leaky buckets */
void throttle_leak_bucket(LeakyBucket *bkt, int64_t delta);
int64_t throttle_compute_wait(LeakyBucket *bkt);
/* expose timer computation function for unit tests */
bool throttle_compute_timer(ThrottleState *ts,
bool is_write,
int64_t now,
int64_t *next_timestamp);
/* init/destroy cycle */
void throttle_init(ThrottleState *ts,
QEMUClockType clock_type,
void (read_timer)(void *),
void (write_timer)(void *),
void *timer_opaque);
void throttle_destroy(ThrottleState *ts);
bool throttle_have_timer(ThrottleState *ts);
/* configuration */
bool throttle_enabled(ThrottleConfig *cfg);
bool throttle_conflicting(ThrottleConfig *cfg);
bool throttle_is_valid(ThrottleConfig *cfg);
void throttle_config(ThrottleState *ts, ThrottleConfig *cfg);
void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg);
/* usage */
bool throttle_schedule_timer(ThrottleState *ts, bool is_write);
void throttle_account(ThrottleState *ts, bool is_write, uint64_t size);