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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 "qemu/aio.h"
29 #include "qapi/qapi-types-block-core.h"
30 #include "qemu/timer.h"
31
32 #define THROTTLE_VALUE_MAX 1000000000000000LL
33
34 typedef enum {
35 THROTTLE_BPS_TOTAL,
36 THROTTLE_BPS_READ,
37 THROTTLE_BPS_WRITE,
38 THROTTLE_OPS_TOTAL,
39 THROTTLE_OPS_READ,
40 THROTTLE_OPS_WRITE,
41 BUCKETS_COUNT,
42 } BucketType;
43
44 /*
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.
48 *
49 * Three parameters can be set by the user:
50 *
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.
54 *
55 * Here's how it works:
56 *
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.
59 *
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.
63 *
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
68 * per second.
69 *
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.
74 *
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
77 * do bursts again.
78 */
79
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 */
86 } LeakyBucket;
87
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.
92 */
93 typedef struct ThrottleConfig {
94 LeakyBucket buckets[BUCKETS_COUNT]; /* leaky buckets */
95 uint64_t op_size; /* size of an operation in bytes */
96 } ThrottleConfig;
97
98 typedef struct ThrottleState {
99 ThrottleConfig cfg; /* configuration */
100 int64_t previous_leak; /* timestamp of the last leak done */
101 } ThrottleState;
102
103 typedef enum {
104 THROTTLE_READ = 0,
105 THROTTLE_WRITE,
106 THROTTLE_MAX
107 } ThrottleDirection;
108
109 typedef struct ThrottleTimers {
110 QEMUTimer *timers[THROTTLE_MAX]; /* timers used to do the throttling */
111 QEMUClockType clock_type; /* the clock used */
112
113 /* Callbacks */
114 QEMUTimerCB *timer_cb[THROTTLE_MAX];
115 void *timer_opaque;
116 } ThrottleTimers;
117
118 /* operations on single leaky buckets */
119 void throttle_leak_bucket(LeakyBucket *bkt, int64_t delta);
120
121 int64_t throttle_compute_wait(LeakyBucket *bkt);
122
123 /* init/destroy cycle */
124 void throttle_init(ThrottleState *ts);
125
126 void throttle_timers_init(ThrottleTimers *tt,
127 AioContext *aio_context,
128 QEMUClockType clock_type,
129 QEMUTimerCB *read_timer_cb,
130 QEMUTimerCB *write_timer_cb,
131 void *timer_opaque);
132
133 void throttle_timers_destroy(ThrottleTimers *tt);
134
135 void throttle_timers_detach_aio_context(ThrottleTimers *tt);
136
137 void throttle_timers_attach_aio_context(ThrottleTimers *tt,
138 AioContext *new_context);
139
140 bool throttle_timers_are_initialized(ThrottleTimers *tt);
141
142 /* configuration */
143 bool throttle_enabled(ThrottleConfig *cfg);
144
145 bool throttle_is_valid(ThrottleConfig *cfg, Error **errp);
146
147 void throttle_config(ThrottleState *ts,
148 QEMUClockType clock_type,
149 ThrottleConfig *cfg);
150
151 void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg);
152
153 void throttle_config_init(ThrottleConfig *cfg);
154
155 /* usage */
156 bool throttle_schedule_timer(ThrottleState *ts,
157 ThrottleTimers *tt,
158 ThrottleDirection direction);
159
160 void throttle_account(ThrottleState *ts, ThrottleDirection direction,
161 uint64_t size);
162 void throttle_limits_to_config(ThrottleLimits *arg, ThrottleConfig *cfg,
163 Error **errp);
164 void throttle_config_to_limits(ThrottleConfig *cfg, ThrottleLimits *var);
165
166 #endif