diff options
Diffstat (limited to '')
| -rw-r--r-- | block/blk-rq-qos.c | 296 |
1 files changed, 296 insertions, 0 deletions
diff --git a/block/blk-rq-qos.c b/block/blk-rq-qos.c new file mode 100644 index 000000000..88f0fe7dc --- /dev/null +++ b/block/blk-rq-qos.c @@ -0,0 +1,296 @@ +// SPDX-License-Identifier: GPL-2.0 + +#include "blk-rq-qos.h" + +/* + * Increment 'v', if 'v' is below 'below'. Returns true if we succeeded, + * false if 'v' + 1 would be bigger than 'below'. + */ +static bool atomic_inc_below(atomic_t *v, unsigned int below) +{ + unsigned int cur = atomic_read(v); + + do { + if (cur >= below) + return false; + } while (!atomic_try_cmpxchg(v, &cur, cur + 1)); + + return true; +} + +bool rq_wait_inc_below(struct rq_wait *rq_wait, unsigned int limit) +{ + return atomic_inc_below(&rq_wait->inflight, limit); +} + +void __rq_qos_cleanup(struct rq_qos *rqos, struct bio *bio) +{ + do { + if (rqos->ops->cleanup) + rqos->ops->cleanup(rqos, bio); + rqos = rqos->next; + } while (rqos); +} + +void __rq_qos_done(struct rq_qos *rqos, struct request *rq) +{ + do { + if (rqos->ops->done) + rqos->ops->done(rqos, rq); + rqos = rqos->next; + } while (rqos); +} + +void __rq_qos_issue(struct rq_qos *rqos, struct request *rq) +{ + do { + if (rqos->ops->issue) + rqos->ops->issue(rqos, rq); + rqos = rqos->next; + } while (rqos); +} + +void __rq_qos_requeue(struct rq_qos *rqos, struct request *rq) +{ + do { + if (rqos->ops->requeue) + rqos->ops->requeue(rqos, rq); + rqos = rqos->next; + } while (rqos); +} + +void __rq_qos_throttle(struct rq_qos *rqos, struct bio *bio) +{ + do { + if (rqos->ops->throttle) + rqos->ops->throttle(rqos, bio); + rqos = rqos->next; + } while (rqos); +} + +void __rq_qos_track(struct rq_qos *rqos, struct request *rq, struct bio *bio) +{ + do { + if (rqos->ops->track) + rqos->ops->track(rqos, rq, bio); + rqos = rqos->next; + } while (rqos); +} + +void __rq_qos_merge(struct rq_qos *rqos, struct request *rq, struct bio *bio) +{ + do { + if (rqos->ops->merge) + rqos->ops->merge(rqos, rq, bio); + rqos = rqos->next; + } while (rqos); +} + +void __rq_qos_done_bio(struct rq_qos *rqos, struct bio *bio) +{ + do { + if (rqos->ops->done_bio) + rqos->ops->done_bio(rqos, bio); + rqos = rqos->next; + } while (rqos); +} + +void __rq_qos_queue_depth_changed(struct rq_qos *rqos) +{ + do { + if (rqos->ops->queue_depth_changed) + rqos->ops->queue_depth_changed(rqos); + rqos = rqos->next; + } while (rqos); +} + +/* + * Return true, if we can't increase the depth further by scaling + */ +bool rq_depth_calc_max_depth(struct rq_depth *rqd) +{ + unsigned int depth; + bool ret = false; + + /* + * For QD=1 devices, this is a special case. It's important for those + * to have one request ready when one completes, so force a depth of + * 2 for those devices. On the backend, it'll be a depth of 1 anyway, + * since the device can't have more than that in flight. If we're + * scaling down, then keep a setting of 1/1/1. + */ + if (rqd->queue_depth == 1) { + if (rqd->scale_step > 0) + rqd->max_depth = 1; + else { + rqd->max_depth = 2; + ret = true; + } + } else { + /* + * scale_step == 0 is our default state. If we have suffered + * latency spikes, step will be > 0, and we shrink the + * allowed write depths. If step is < 0, we're only doing + * writes, and we allow a temporarily higher depth to + * increase performance. + */ + depth = min_t(unsigned int, rqd->default_depth, + rqd->queue_depth); + if (rqd->scale_step > 0) + depth = 1 + ((depth - 1) >> min(31, rqd->scale_step)); + else if (rqd->scale_step < 0) { + unsigned int maxd = 3 * rqd->queue_depth / 4; + + depth = 1 + ((depth - 1) << -rqd->scale_step); + if (depth > maxd) { + depth = maxd; + ret = true; + } + } + + rqd->max_depth = depth; + } + + return ret; +} + +/* Returns true on success and false if scaling up wasn't possible */ +bool rq_depth_scale_up(struct rq_depth *rqd) +{ + /* + * Hit max in previous round, stop here + */ + if (rqd->scaled_max) + return false; + + rqd->scale_step--; + + rqd->scaled_max = rq_depth_calc_max_depth(rqd); + return true; +} + +/* + * Scale rwb down. If 'hard_throttle' is set, do it quicker, since we + * had a latency violation. Returns true on success and returns false if + * scaling down wasn't possible. + */ +bool rq_depth_scale_down(struct rq_depth *rqd, bool hard_throttle) +{ + /* + * Stop scaling down when we've hit the limit. This also prevents + * ->scale_step from going to crazy values, if the device can't + * keep up. + */ + if (rqd->max_depth == 1) + return false; + + if (rqd->scale_step < 0 && hard_throttle) + rqd->scale_step = 0; + else + rqd->scale_step++; + + rqd->scaled_max = false; + rq_depth_calc_max_depth(rqd); + return true; +} + +struct rq_qos_wait_data { + struct wait_queue_entry wq; + struct task_struct *task; + struct rq_wait *rqw; + acquire_inflight_cb_t *cb; + void *private_data; + bool got_token; +}; + +static int rq_qos_wake_function(struct wait_queue_entry *curr, + unsigned int mode, int wake_flags, void *key) +{ + struct rq_qos_wait_data *data = container_of(curr, + struct rq_qos_wait_data, + wq); + + /* + * If we fail to get a budget, return -1 to interrupt the wake up loop + * in __wake_up_common. + */ + if (!data->cb(data->rqw, data->private_data)) + return -1; + + data->got_token = true; + smp_wmb(); + list_del_init(&curr->entry); + wake_up_process(data->task); + return 1; +} + +/** + * rq_qos_wait - throttle on a rqw if we need to + * @rqw: rqw to throttle on + * @private_data: caller provided specific data + * @acquire_inflight_cb: inc the rqw->inflight counter if we can + * @cleanup_cb: the callback to cleanup in case we race with a waker + * + * This provides a uniform place for the rq_qos users to do their throttling. + * Since you can end up with a lot of things sleeping at once, this manages the + * waking up based on the resources available. The acquire_inflight_cb should + * inc the rqw->inflight if we have the ability to do so, or return false if not + * and then we will sleep until the room becomes available. + * + * cleanup_cb is in case that we race with a waker and need to cleanup the + * inflight count accordingly. + */ +void rq_qos_wait(struct rq_wait *rqw, void *private_data, + acquire_inflight_cb_t *acquire_inflight_cb, + cleanup_cb_t *cleanup_cb) +{ + struct rq_qos_wait_data data = { + .wq = { + .func = rq_qos_wake_function, + .entry = LIST_HEAD_INIT(data.wq.entry), + }, + .task = current, + .rqw = rqw, + .cb = acquire_inflight_cb, + .private_data = private_data, + }; + bool has_sleeper; + + has_sleeper = wq_has_sleeper(&rqw->wait); + if (!has_sleeper && acquire_inflight_cb(rqw, private_data)) + return; + + has_sleeper = !prepare_to_wait_exclusive(&rqw->wait, &data.wq, + TASK_UNINTERRUPTIBLE); + do { + /* The memory barrier in set_task_state saves us here. */ + if (data.got_token) + break; + if (!has_sleeper && acquire_inflight_cb(rqw, private_data)) { + finish_wait(&rqw->wait, &data.wq); + + /* + * We raced with wbt_wake_function() getting a token, + * which means we now have two. Put our local token + * and wake anyone else potentially waiting for one. + */ + smp_rmb(); + if (data.got_token) + cleanup_cb(rqw, private_data); + break; + } + io_schedule(); + has_sleeper = true; + set_current_state(TASK_UNINTERRUPTIBLE); + } while (1); + finish_wait(&rqw->wait, &data.wq); +} + +void rq_qos_exit(struct request_queue *q) +{ + while (q->rq_qos) { + struct rq_qos *rqos = q->rq_qos; + q->rq_qos = rqos->next; + rqos->ops->exit(rqos); + } +} |