159 lines
5.5 KiB
C
159 lines
5.5 KiB
C
/*
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* QEMU throttling infrastructure
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*
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* Copyright (C) Nodalink, EURL. 2013-2014
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* Copyright (C) Igalia, S.L. 2015-2016
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*
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* Authors:
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* Benoît Canet <benoit.canet@nodalink.com>
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* Alberto Garcia <berto@igalia.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation; either version 2 or
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* (at your option) version 3 of the License.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef THROTTLE_H
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#define THROTTLE_H
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#include "qapi/qapi-types-block-core.h"
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#include "qemu/timer.h"
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#define THROTTLE_VALUE_MAX 1000000000000000LL
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typedef enum {
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THROTTLE_BPS_TOTAL,
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THROTTLE_BPS_READ,
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THROTTLE_BPS_WRITE,
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THROTTLE_OPS_TOTAL,
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THROTTLE_OPS_READ,
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THROTTLE_OPS_WRITE,
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BUCKETS_COUNT,
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} BucketType;
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/*
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* This module implements I/O limits using the leaky bucket
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* algorithm. The code is independent of the I/O units, but it is
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* currently used for bytes per second and operations per second.
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*
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* Three parameters can be set by the user:
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*
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* - avg: the desired I/O limits in units per second.
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* - max: the limit during bursts, also in units per second.
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* - burst_length: the maximum length of the burst period, in seconds.
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*
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* Here's how it works:
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*
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* - The bucket level (number of performed I/O units) is kept in
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* bkt.level and leaks at a rate of bkt.avg units per second.
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*
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* - The size of the bucket is bkt.max * bkt.burst_length. Once the
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* bucket is full no more I/O is performed until the bucket leaks
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* again. This is what makes the I/O rate bkt.avg.
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*
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* - The bkt.avg rate does not apply until the bucket is full,
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* allowing the user to do bursts until then. The I/O limit during
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* bursts is bkt.max. To enforce this limit we keep an additional
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* bucket in bkt.burst_level that leaks at a rate of bkt.max units
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* per second.
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*
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* - Because of all of the above, the user can perform I/O at a
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* maximum of bkt.max units per second for at most bkt.burst_length
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* seconds in a row. After that the bucket will be full and the I/O
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* rate will go down to bkt.avg.
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*
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* - Since the bucket always leaks at a rate of bkt.avg, this also
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* determines how much the user needs to wait before being able to
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* do bursts again.
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*/
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typedef struct LeakyBucket {
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uint64_t avg; /* average goal in units per second */
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uint64_t max; /* leaky bucket max burst in units */
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double level; /* bucket level in units */
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double burst_level; /* bucket level in units (for computing bursts) */
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uint64_t burst_length; /* max length of the burst period, in seconds */
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} LeakyBucket;
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/* The following structure is used to configure a ThrottleState
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* It contains a bit of state: the bucket field of the LeakyBucket structure.
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* However it allows to keep the code clean and the bucket field is reset to
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* zero at the right time.
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*/
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typedef struct ThrottleConfig {
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LeakyBucket buckets[BUCKETS_COUNT]; /* leaky buckets */
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uint64_t op_size; /* size of an operation in bytes */
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} ThrottleConfig;
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typedef struct ThrottleState {
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ThrottleConfig cfg; /* configuration */
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int64_t previous_leak; /* timestamp of the last leak done */
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} ThrottleState;
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typedef struct ThrottleTimers {
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QEMUTimer *timers[2]; /* timers used to do the throttling */
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QEMUClockType clock_type; /* the clock used */
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/* Callbacks */
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QEMUTimerCB *read_timer_cb;
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QEMUTimerCB *write_timer_cb;
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void *timer_opaque;
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} ThrottleTimers;
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/* operations on single leaky buckets */
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void throttle_leak_bucket(LeakyBucket *bkt, int64_t delta);
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int64_t throttle_compute_wait(LeakyBucket *bkt);
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/* init/destroy cycle */
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void throttle_init(ThrottleState *ts);
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void throttle_timers_init(ThrottleTimers *tt,
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AioContext *aio_context,
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QEMUClockType clock_type,
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QEMUTimerCB *read_timer_cb,
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QEMUTimerCB *write_timer_cb,
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void *timer_opaque);
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void throttle_timers_destroy(ThrottleTimers *tt);
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void throttle_timers_detach_aio_context(ThrottleTimers *tt);
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void throttle_timers_attach_aio_context(ThrottleTimers *tt,
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AioContext *new_context);
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bool throttle_timers_are_initialized(ThrottleTimers *tt);
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/* configuration */
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bool throttle_enabled(ThrottleConfig *cfg);
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bool throttle_is_valid(ThrottleConfig *cfg, Error **errp);
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void throttle_config(ThrottleState *ts,
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QEMUClockType clock_type,
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ThrottleConfig *cfg);
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void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg);
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void throttle_config_init(ThrottleConfig *cfg);
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/* usage */
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bool throttle_schedule_timer(ThrottleState *ts,
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ThrottleTimers *tt,
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bool is_write);
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void throttle_account(ThrottleState *ts, bool is_write, uint64_t size);
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void throttle_limits_to_config(ThrottleLimits *arg, ThrottleConfig *cfg,
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Error **errp);
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void throttle_config_to_limits(ThrottleConfig *cfg, ThrottleLimits *var);
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#endif
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