]>
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2 * QEMU throttling infrastructure
4 * Copyright (C) Nodalink, EURL. 2013-2014
5 * Copyright (C) Igalia, S.L. 2015-2016
8 * BenoƮt Canet <benoit.canet@nodalink.com>
9 * Alberto Garcia <berto@igalia.com>
11 * This program is free software; you can redistribute it and/or
12 * modify it under the terms of the GNU General Public License as
13 * published by the Free Software Foundation; either version 2 or
14 * (at your option) version 3 of the License.
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
21 * You should have received a copy of the GNU General Public License
22 * along with this program; if not, see <http://www.gnu.org/licenses/>.
28 #include "qemu-common.h"
29 #include "qapi/qapi-types-block-core.h"
30 #include "qemu/timer.h"
32 #define THROTTLE_VALUE_MAX 1000000000000000LL
45 * This module implements I/O limits using the leaky bucket
46 * algorithm. The code is independent of the I/O units, but it is
47 * currently used for bytes per second and operations per second.
49 * Three parameters can be set by the user:
51 * - avg: the desired I/O limits in units per second.
52 * - max: the limit during bursts, also in units per second.
53 * - burst_length: the maximum length of the burst period, in seconds.
55 * Here's how it works:
57 * - The bucket level (number of performed I/O units) is kept in
58 * bkt.level and leaks at a rate of bkt.avg units per second.
60 * - The size of the bucket is bkt.max * bkt.burst_length. Once the
61 * bucket is full no more I/O is performed until the bucket leaks
62 * again. This is what makes the I/O rate bkt.avg.
64 * - The bkt.avg rate does not apply until the bucket is full,
65 * allowing the user to do bursts until then. The I/O limit during
66 * bursts is bkt.max. To enforce this limit we keep an additional
67 * bucket in bkt.burst_level that leaks at a rate of bkt.max units
70 * - Because of all of the above, the user can perform I/O at a
71 * maximum of bkt.max units per second for at most bkt.burst_length
72 * seconds in a row. After that the bucket will be full and the I/O
73 * rate will go down to bkt.avg.
75 * - Since the bucket always leaks at a rate of bkt.avg, this also
76 * determines how much the user needs to wait before being able to
80 typedef struct LeakyBucket
{
81 uint64_t avg
; /* average goal in units per second */
82 uint64_t max
; /* leaky bucket max burst in units */
83 double level
; /* bucket level in units */
84 double burst_level
; /* bucket level in units (for computing bursts) */
85 uint64_t burst_length
; /* max length of the burst period, in seconds */
88 /* The following structure is used to configure a ThrottleState
89 * It contains a bit of state: the bucket field of the LeakyBucket structure.
90 * However it allows to keep the code clean and the bucket field is reset to
91 * zero at the right time.
93 typedef struct ThrottleConfig
{
94 LeakyBucket buckets
[BUCKETS_COUNT
]; /* leaky buckets */
95 uint64_t op_size
; /* size of an operation in bytes */
98 typedef struct ThrottleState
{
99 ThrottleConfig cfg
; /* configuration */
100 int64_t previous_leak
; /* timestamp of the last leak done */
103 typedef struct ThrottleTimers
{
104 QEMUTimer
*timers
[2]; /* timers used to do the throttling */
105 QEMUClockType clock_type
; /* the clock used */
108 QEMUTimerCB
*read_timer_cb
;
109 QEMUTimerCB
*write_timer_cb
;
113 /* operations on single leaky buckets */
114 void throttle_leak_bucket(LeakyBucket
*bkt
, int64_t delta
);
116 int64_t throttle_compute_wait(LeakyBucket
*bkt
);
118 /* init/destroy cycle */
119 void throttle_init(ThrottleState
*ts
);
121 void throttle_timers_init(ThrottleTimers
*tt
,
122 AioContext
*aio_context
,
123 QEMUClockType clock_type
,
124 QEMUTimerCB
*read_timer_cb
,
125 QEMUTimerCB
*write_timer_cb
,
128 void throttle_timers_destroy(ThrottleTimers
*tt
);
130 void throttle_timers_detach_aio_context(ThrottleTimers
*tt
);
132 void throttle_timers_attach_aio_context(ThrottleTimers
*tt
,
133 AioContext
*new_context
);
135 bool throttle_timers_are_initialized(ThrottleTimers
*tt
);
138 bool throttle_enabled(ThrottleConfig
*cfg
);
140 bool throttle_is_valid(ThrottleConfig
*cfg
, Error
**errp
);
142 void throttle_config(ThrottleState
*ts
,
143 QEMUClockType clock_type
,
144 ThrottleConfig
*cfg
);
146 void throttle_get_config(ThrottleState
*ts
, ThrottleConfig
*cfg
);
148 void throttle_config_init(ThrottleConfig
*cfg
);
151 bool throttle_schedule_timer(ThrottleState
*ts
,
155 void throttle_account(ThrottleState
*ts
, bool is_write
, uint64_t size
);
156 void throttle_limits_to_config(ThrottleLimits
*arg
, ThrottleConfig
*cfg
,
158 void throttle_config_to_limits(ThrottleConfig
*cfg
, ThrottleLimits
*var
);