1/*
2 * QEMU throttling infrastructure
3 *
4 * Copyright (C) Nodalink, EURL. 2013-2014
5 * Copyright (C) Igalia, S.L. 2015-2016
6 *
7 * Authors:
8 * Benoît Canet <benoit.canet@nodalink.com>
9 * Alberto Garcia <berto@igalia.com>
10 *
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.
15 *
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.
20 *
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/>.
23 */
24
25#ifndef THROTTLE_H
26#define THROTTLE_H
27
28#include "qapi/qapi-types-block-core.h"
29#include "qemu/timer.h"
30
31#define THROTTLE_VALUE_MAX 1000000000000000LL
32
33typedef enum {
34 THROTTLE_BPS_TOTAL,
35 THROTTLE_BPS_READ,
36 THROTTLE_BPS_WRITE,
37 THROTTLE_OPS_TOTAL,
38 THROTTLE_OPS_READ,
39 THROTTLE_OPS_WRITE,
40 BUCKETS_COUNT,
41} BucketType;
42
43/*
44 * This module implements I/O limits using the leaky bucket
45 * algorithm. The code is independent of the I/O units, but it is
46 * currently used for bytes per second and operations per second.
47 *
48 * Three parameters can be set by the user:
49 *
50 * - avg: the desired I/O limits in units per second.
51 * - max: the limit during bursts, also in units per second.
52 * - burst_length: the maximum length of the burst period, in seconds.
53 *
54 * Here's how it works:
55 *
56 * - The bucket level (number of performed I/O units) is kept in
57 * bkt.level and leaks at a rate of bkt.avg units per second.
58 *
59 * - The size of the bucket is bkt.max * bkt.burst_length. Once the
60 * bucket is full no more I/O is performed until the bucket leaks
61 * again. This is what makes the I/O rate bkt.avg.
62 *
63 * - The bkt.avg rate does not apply until the bucket is full,
64 * allowing the user to do bursts until then. The I/O limit during
65 * bursts is bkt.max. To enforce this limit we keep an additional
66 * bucket in bkt.burst_level that leaks at a rate of bkt.max units
67 * per second.
68 *
69 * - Because of all of the above, the user can perform I/O at a
70 * maximum of bkt.max units per second for at most bkt.burst_length
71 * seconds in a row. After that the bucket will be full and the I/O
72 * rate will go down to bkt.avg.
73 *
74 * - Since the bucket always leaks at a rate of bkt.avg, this also
75 * determines how much the user needs to wait before being able to
76 * do bursts again.
77 */
78
79typedef struct LeakyBucket {
80 uint64_t avg; /* average goal in units per second */
81 uint64_t max; /* leaky bucket max burst in units */
82 double level; /* bucket level in units */
83 double burst_level; /* bucket level in units (for computing bursts) */
84 uint64_t burst_length; /* max length of the burst period, in seconds */
85} LeakyBucket;
86
87/* The following structure is used to configure a ThrottleState
88 * It contains a bit of state: the bucket field of the LeakyBucket structure.
89 * However it allows to keep the code clean and the bucket field is reset to
90 * zero at the right time.
91 */
92typedef struct ThrottleConfig {
93 LeakyBucket buckets[BUCKETS_COUNT]; /* leaky buckets */
94 uint64_t op_size; /* size of an operation in bytes */
95} ThrottleConfig;
96
97typedef struct ThrottleState {
98 ThrottleConfig cfg; /* configuration */
99 int64_t previous_leak; /* timestamp of the last leak done */
100} ThrottleState;
101
102typedef struct ThrottleTimers {
103 QEMUTimer *timers[2]; /* timers used to do the throttling */
104 QEMUClockType clock_type; /* the clock used */
105
106 /* Callbacks */
107 QEMUTimerCB *read_timer_cb;
108 QEMUTimerCB *write_timer_cb;
109 void *timer_opaque;
110} ThrottleTimers;
111
112/* operations on single leaky buckets */
113void throttle_leak_bucket(LeakyBucket *bkt, int64_t delta);
114
115int64_t throttle_compute_wait(LeakyBucket *bkt);
116
117/* init/destroy cycle */
118void throttle_init(ThrottleState *ts);
119
120void throttle_timers_init(ThrottleTimers *tt,
121 AioContext *aio_context,
122 QEMUClockType clock_type,
123 QEMUTimerCB *read_timer_cb,
124 QEMUTimerCB *write_timer_cb,
125 void *timer_opaque);
126
127void throttle_timers_destroy(ThrottleTimers *tt);
128
129void throttle_timers_detach_aio_context(ThrottleTimers *tt);
130
131void throttle_timers_attach_aio_context(ThrottleTimers *tt,
132 AioContext *new_context);
133
134bool throttle_timers_are_initialized(ThrottleTimers *tt);
135
136/* configuration */
137bool throttle_enabled(ThrottleConfig *cfg);
138
139bool throttle_is_valid(ThrottleConfig *cfg, Error **errp);
140
141void throttle_config(ThrottleState *ts,
142 QEMUClockType clock_type,
143 ThrottleConfig *cfg);
144
145void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg);
146
147void throttle_config_init(ThrottleConfig *cfg);
148
149/* usage */
150bool throttle_schedule_timer(ThrottleState *ts,
151 ThrottleTimers *tt,
152 bool is_write);
153
154void throttle_account(ThrottleState *ts, bool is_write, uint64_t size);
155void throttle_limits_to_config(ThrottleLimits *arg, ThrottleConfig *cfg,
156 Error **errp);
157void throttle_config_to_limits(ThrottleConfig *cfg, ThrottleLimits *var);
158
159#endif
160