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-common.h" 29 #include "qemu/timer.h" 30 31 #define THROTTLE_VALUE_MAX 1000000000000000LL 32 33 typedef 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 79 typedef 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 */ 92 typedef struct ThrottleConfig { 93 LeakyBucket buckets[BUCKETS_COUNT]; /* leaky buckets */ 94 uint64_t op_size; /* size of an operation in bytes */ 95 } ThrottleConfig; 96 97 typedef struct ThrottleState { 98 ThrottleConfig cfg; /* configuration */ 99 int64_t previous_leak; /* timestamp of the last leak done */ 100 } ThrottleState; 101 102 typedef 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 */ 113 void throttle_leak_bucket(LeakyBucket *bkt, int64_t delta); 114 115 int64_t throttle_compute_wait(LeakyBucket *bkt); 116 117 /* init/destroy cycle */ 118 void throttle_init(ThrottleState *ts); 119 120 void 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); 126 127 void throttle_timers_destroy(ThrottleTimers *tt); 128 129 void throttle_timers_detach_aio_context(ThrottleTimers *tt); 130 131 void throttle_timers_attach_aio_context(ThrottleTimers *tt, 132 AioContext *new_context); 133 134 bool throttle_timers_are_initialized(ThrottleTimers *tt); 135 136 /* configuration */ 137 bool throttle_enabled(ThrottleConfig *cfg); 138 139 bool throttle_is_valid(ThrottleConfig *cfg, Error **errp); 140 141 void throttle_config(ThrottleState *ts, 142 QEMUClockType clock_type, 143 ThrottleConfig *cfg); 144 145 void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg); 146 147 void throttle_config_init(ThrottleConfig *cfg); 148 149 /* usage */ 150 bool throttle_schedule_timer(ThrottleState *ts, 151 ThrottleTimers *tt, 152 bool is_write); 153 154 void throttle_account(ThrottleState *ts, bool is_write, uint64_t size); 155 void throttle_limits_to_config(ThrottleLimits *arg, ThrottleConfig *cfg, 156 Error **errp); 157 void throttle_config_to_limits(ThrottleConfig *cfg, ThrottleLimits *var); 158 159 #endif 160