/* * QEMU throttling infrastructure * * Copyright (C) Nodalink, EURL. 2013-2014 * Copyright (C) Igalia, S.L. 2015-2016 * * Authors: * BenoƮt Canet * Alberto Garcia * * 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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * 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 "qapi/qapi-types-block-core.h" #include "qemu/timer.h" #define THROTTLE_VALUE_MAX 1000000000000000LL typedef enum { THROTTLE_BPS_TOTAL, THROTTLE_BPS_READ, THROTTLE_BPS_WRITE, THROTTLE_OPS_TOTAL, THROTTLE_OPS_READ, THROTTLE_OPS_WRITE, BUCKETS_COUNT, } BucketType; /* * This module implements I/O limits using the leaky bucket * algorithm. The code is independent of the I/O units, but it is * currently used for bytes per second and operations per second. * * Three parameters can be set by the user: * * - avg: the desired I/O limits in units per second. * - max: the limit during bursts, also in units per second. * - burst_length: the maximum length of the burst period, in seconds. * * Here's how it works: * * - The bucket level (number of performed I/O units) is kept in * bkt.level and leaks at a rate of bkt.avg units per second. * * - The size of the bucket is bkt.max * bkt.burst_length. Once the * bucket is full no more I/O is performed until the bucket leaks * again. This is what makes the I/O rate bkt.avg. * * - The bkt.avg rate does not apply until the bucket is full, * allowing the user to do bursts until then. The I/O limit during * bursts is bkt.max. To enforce this limit we keep an additional * bucket in bkt.burst_level that leaks at a rate of bkt.max units * per second. * * - Because of all of the above, the user can perform I/O at a * maximum of bkt.max units per second for at most bkt.burst_length * seconds in a row. After that the bucket will be full and the I/O * rate will go down to bkt.avg. * * - Since the bucket always leaks at a rate of bkt.avg, this also * determines how much the user needs to wait before being able to * do bursts again. */ typedef struct LeakyBucket { uint64_t avg; /* average goal in units per second */ uint64_t max; /* leaky bucket max burst in units */ double level; /* bucket level in units */ double burst_level; /* bucket level in units (for computing bursts) */ uint64_t burst_length; /* max length of the burst period, in seconds */ } 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 */ } ThrottleState; typedef enum { THROTTLE_READ = 0, THROTTLE_WRITE, THROTTLE_MAX } ThrottleDirection; typedef struct ThrottleTimers { QEMUTimer *timers[THROTTLE_MAX]; /* timers used to do the throttling */ QEMUClockType clock_type; /* the clock used */ /* Callbacks */ QEMUTimerCB *timer_cb[THROTTLE_MAX]; void *timer_opaque; } ThrottleTimers; /* operations on single leaky buckets */ void throttle_leak_bucket(LeakyBucket *bkt, int64_t delta); int64_t throttle_compute_wait(LeakyBucket *bkt); /* init/destroy cycle */ void throttle_init(ThrottleState *ts); void throttle_timers_init(ThrottleTimers *tt, AioContext *aio_context, QEMUClockType clock_type, QEMUTimerCB *read_timer_cb, QEMUTimerCB *write_timer_cb, void *timer_opaque); void throttle_timers_destroy(ThrottleTimers *tt); void throttle_timers_detach_aio_context(ThrottleTimers *tt); void throttle_timers_attach_aio_context(ThrottleTimers *tt, AioContext *new_context); bool throttle_timers_are_initialized(ThrottleTimers *tt); /* configuration */ bool throttle_enabled(ThrottleConfig *cfg); bool throttle_is_valid(ThrottleConfig *cfg, Error **errp); void throttle_config(ThrottleState *ts, QEMUClockType clock_type, ThrottleConfig *cfg); void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg); void throttle_config_init(ThrottleConfig *cfg); /* usage */ bool throttle_schedule_timer(ThrottleState *ts, ThrottleTimers *tt, ThrottleDirection direction); void throttle_account(ThrottleState *ts, ThrottleDirection direction, uint64_t size); void throttle_limits_to_config(ThrottleLimits *arg, ThrottleConfig *cfg, Error **errp); void throttle_config_to_limits(ThrottleConfig *cfg, ThrottleLimits *var); #endif