1 // SPDX-License-Identifier: GPL-2.0 2 3 #include "blk-rq-qos.h" 4 5 /* 6 * Increment 'v', if 'v' is below 'below'. Returns true if we succeeded, 7 * false if 'v' + 1 would be bigger than 'below'. 8 */ 9 static bool atomic_inc_below(atomic_t *v, unsigned int below) 10 { 11 unsigned int cur = atomic_read(v); 12 13 do { 14 if (cur >= below) 15 return false; 16 } while (!atomic_try_cmpxchg(v, &cur, cur + 1)); 17 18 return true; 19 } 20 21 bool rq_wait_inc_below(struct rq_wait *rq_wait, unsigned int limit) 22 { 23 return atomic_inc_below(&rq_wait->inflight, limit); 24 } 25 26 void __rq_qos_cleanup(struct rq_qos *rqos, struct bio *bio) 27 { 28 do { 29 if (rqos->ops->cleanup) 30 rqos->ops->cleanup(rqos, bio); 31 rqos = rqos->next; 32 } while (rqos); 33 } 34 35 void __rq_qos_done(struct rq_qos *rqos, struct request *rq) 36 { 37 do { 38 if (rqos->ops->done) 39 rqos->ops->done(rqos, rq); 40 rqos = rqos->next; 41 } while (rqos); 42 } 43 44 void __rq_qos_issue(struct rq_qos *rqos, struct request *rq) 45 { 46 do { 47 if (rqos->ops->issue) 48 rqos->ops->issue(rqos, rq); 49 rqos = rqos->next; 50 } while (rqos); 51 } 52 53 void __rq_qos_requeue(struct rq_qos *rqos, struct request *rq) 54 { 55 do { 56 if (rqos->ops->requeue) 57 rqos->ops->requeue(rqos, rq); 58 rqos = rqos->next; 59 } while (rqos); 60 } 61 62 void __rq_qos_throttle(struct rq_qos *rqos, struct bio *bio) 63 { 64 do { 65 if (rqos->ops->throttle) 66 rqos->ops->throttle(rqos, bio); 67 rqos = rqos->next; 68 } while (rqos); 69 } 70 71 void __rq_qos_track(struct rq_qos *rqos, struct request *rq, struct bio *bio) 72 { 73 do { 74 if (rqos->ops->track) 75 rqos->ops->track(rqos, rq, bio); 76 rqos = rqos->next; 77 } while (rqos); 78 } 79 80 void __rq_qos_merge(struct rq_qos *rqos, struct request *rq, struct bio *bio) 81 { 82 do { 83 if (rqos->ops->merge) 84 rqos->ops->merge(rqos, rq, bio); 85 rqos = rqos->next; 86 } while (rqos); 87 } 88 89 void __rq_qos_done_bio(struct rq_qos *rqos, struct bio *bio) 90 { 91 do { 92 if (rqos->ops->done_bio) 93 rqos->ops->done_bio(rqos, bio); 94 rqos = rqos->next; 95 } while (rqos); 96 } 97 98 void __rq_qos_queue_depth_changed(struct rq_qos *rqos) 99 { 100 do { 101 if (rqos->ops->queue_depth_changed) 102 rqos->ops->queue_depth_changed(rqos); 103 rqos = rqos->next; 104 } while (rqos); 105 } 106 107 /* 108 * Return true, if we can't increase the depth further by scaling 109 */ 110 bool rq_depth_calc_max_depth(struct rq_depth *rqd) 111 { 112 unsigned int depth; 113 bool ret = false; 114 115 /* 116 * For QD=1 devices, this is a special case. It's important for those 117 * to have one request ready when one completes, so force a depth of 118 * 2 for those devices. On the backend, it'll be a depth of 1 anyway, 119 * since the device can't have more than that in flight. If we're 120 * scaling down, then keep a setting of 1/1/1. 121 */ 122 if (rqd->queue_depth == 1) { 123 if (rqd->scale_step > 0) 124 rqd->max_depth = 1; 125 else { 126 rqd->max_depth = 2; 127 ret = true; 128 } 129 } else { 130 /* 131 * scale_step == 0 is our default state. If we have suffered 132 * latency spikes, step will be > 0, and we shrink the 133 * allowed write depths. If step is < 0, we're only doing 134 * writes, and we allow a temporarily higher depth to 135 * increase performance. 136 */ 137 depth = min_t(unsigned int, rqd->default_depth, 138 rqd->queue_depth); 139 if (rqd->scale_step > 0) 140 depth = 1 + ((depth - 1) >> min(31, rqd->scale_step)); 141 else if (rqd->scale_step < 0) { 142 unsigned int maxd = 3 * rqd->queue_depth / 4; 143 144 depth = 1 + ((depth - 1) << -rqd->scale_step); 145 if (depth > maxd) { 146 depth = maxd; 147 ret = true; 148 } 149 } 150 151 rqd->max_depth = depth; 152 } 153 154 return ret; 155 } 156 157 /* Returns true on success and false if scaling up wasn't possible */ 158 bool rq_depth_scale_up(struct rq_depth *rqd) 159 { 160 /* 161 * Hit max in previous round, stop here 162 */ 163 if (rqd->scaled_max) 164 return false; 165 166 rqd->scale_step--; 167 168 rqd->scaled_max = rq_depth_calc_max_depth(rqd); 169 return true; 170 } 171 172 /* 173 * Scale rwb down. If 'hard_throttle' is set, do it quicker, since we 174 * had a latency violation. Returns true on success and returns false if 175 * scaling down wasn't possible. 176 */ 177 bool rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle) 178 { 179 /* 180 * Stop scaling down when we've hit the limit. This also prevents 181 * ->scale_step from going to crazy values, if the device can't 182 * keep up. 183 */ 184 if (rqd->max_depth == 1) 185 return false; 186 187 if (rqd->scale_step < 0 && hard_throttle) 188 rqd->scale_step = 0; 189 else 190 rqd->scale_step++; 191 192 rqd->scaled_max = false; 193 rq_depth_calc_max_depth(rqd); 194 return true; 195 } 196 197 struct rq_qos_wait_data { 198 struct wait_queue_entry wq; 199 struct task_struct *task; 200 struct rq_wait *rqw; 201 acquire_inflight_cb_t *cb; 202 void *private_data; 203 bool got_token; 204 }; 205 206 static int rq_qos_wake_function(struct wait_queue_entry *curr, 207 unsigned int mode, int wake_flags, void *key) 208 { 209 struct rq_qos_wait_data *data = container_of(curr, 210 struct rq_qos_wait_data, 211 wq); 212 213 /* 214 * If we fail to get a budget, return -1 to interrupt the wake up loop 215 * in __wake_up_common. 216 */ 217 if (!data->cb(data->rqw, data->private_data)) 218 return -1; 219 220 data->got_token = true; 221 smp_wmb(); 222 list_del_init(&curr->entry); 223 wake_up_process(data->task); 224 return 1; 225 } 226 227 /** 228 * rq_qos_wait - throttle on a rqw if we need to 229 * @rqw: rqw to throttle on 230 * @private_data: caller provided specific data 231 * @acquire_inflight_cb: inc the rqw->inflight counter if we can 232 * @cleanup_cb: the callback to cleanup in case we race with a waker 233 * 234 * This provides a uniform place for the rq_qos users to do their throttling. 235 * Since you can end up with a lot of things sleeping at once, this manages the 236 * waking up based on the resources available. The acquire_inflight_cb should 237 * inc the rqw->inflight if we have the ability to do so, or return false if not 238 * and then we will sleep until the room becomes available. 239 * 240 * cleanup_cb is in case that we race with a waker and need to cleanup the 241 * inflight count accordingly. 242 */ 243 void rq_qos_wait(struct rq_wait *rqw, void *private_data, 244 acquire_inflight_cb_t *acquire_inflight_cb, 245 cleanup_cb_t *cleanup_cb) 246 { 247 struct rq_qos_wait_data data = { 248 .wq = { 249 .func = rq_qos_wake_function, 250 .entry = LIST_HEAD_INIT(data.wq.entry), 251 }, 252 .task = current, 253 .rqw = rqw, 254 .cb = acquire_inflight_cb, 255 .private_data = private_data, 256 }; 257 bool has_sleeper; 258 259 has_sleeper = wq_has_sleeper(&rqw->wait); 260 if (!has_sleeper && acquire_inflight_cb(rqw, private_data)) 261 return; 262 263 has_sleeper = !prepare_to_wait_exclusive(&rqw->wait, &data.wq, 264 TASK_UNINTERRUPTIBLE); 265 do { 266 /* The memory barrier in set_task_state saves us here. */ 267 if (data.got_token) 268 break; 269 if (!has_sleeper && acquire_inflight_cb(rqw, private_data)) { 270 finish_wait(&rqw->wait, &data.wq); 271 272 /* 273 * We raced with wbt_wake_function() getting a token, 274 * which means we now have two. Put our local token 275 * and wake anyone else potentially waiting for one. 276 */ 277 smp_rmb(); 278 if (data.got_token) 279 cleanup_cb(rqw, private_data); 280 break; 281 } 282 io_schedule(); 283 has_sleeper = true; 284 set_current_state(TASK_UNINTERRUPTIBLE); 285 } while (1); 286 finish_wait(&rqw->wait, &data.wq); 287 } 288 289 void rq_qos_exit(struct request_queue *q) 290 { 291 while (q->rq_qos) { 292 struct rq_qos *rqos = q->rq_qos; 293 q->rq_qos = rqos->next; 294 rqos->ops->exit(rqos); 295 } 296 } 297