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 <stdint.h> 29 #include "qemu-common.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_length 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 double avg; /* average goal in units per second */ 82 double 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 unsigned 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 struct ThrottleTimers { 104 QEMUTimer *timers[2]; /* timers used to do the throttling */ 105 QEMUClockType clock_type; /* the clock used */ 106 107 /* Callbacks */ 108 QEMUTimerCB *read_timer_cb; 109 QEMUTimerCB *write_timer_cb; 110 void *timer_opaque; 111 } ThrottleTimers; 112 113 /* operations on single leaky buckets */ 114 void throttle_leak_bucket(LeakyBucket *bkt, int64_t delta); 115 116 int64_t throttle_compute_wait(LeakyBucket *bkt); 117 118 /* init/destroy cycle */ 119 void throttle_init(ThrottleState *ts); 120 121 void throttle_timers_init(ThrottleTimers *tt, 122 AioContext *aio_context, 123 QEMUClockType clock_type, 124 QEMUTimerCB *read_timer_cb, 125 QEMUTimerCB *write_timer_cb, 126 void *timer_opaque); 127 128 void throttle_timers_destroy(ThrottleTimers *tt); 129 130 void throttle_timers_detach_aio_context(ThrottleTimers *tt); 131 132 void throttle_timers_attach_aio_context(ThrottleTimers *tt, 133 AioContext *new_context); 134 135 bool throttle_timers_are_initialized(ThrottleTimers *tt); 136 137 /* configuration */ 138 bool throttle_enabled(ThrottleConfig *cfg); 139 140 bool throttle_is_valid(ThrottleConfig *cfg, Error **errp); 141 142 void throttle_config(ThrottleState *ts, 143 ThrottleTimers *tt, 144 ThrottleConfig *cfg); 145 146 void throttle_get_config(ThrottleState *ts, ThrottleConfig *cfg); 147 148 void throttle_config_init(ThrottleConfig *cfg); 149 150 /* usage */ 151 bool throttle_schedule_timer(ThrottleState *ts, 152 ThrottleTimers *tt, 153 bool is_write); 154 155 void throttle_account(ThrottleState *ts, bool is_write, uint64_t size); 156 157 #endif 158