diff --git a/block/mq-deadline.c b/block/mq-deadline.c index b262f40f32c07ec28947f34b2cc978eefa61c9d8..2001ac186f5cd750f91d2b3a81d330fa62310a3c 100644 --- a/block/mq-deadline.c +++ b/block/mq-deadline.c @@ -31,6 +31,11 @@ */ static const int read_expire = HZ / 2; /* max time before a read is submitted. */ static const int write_expire = 5 * HZ; /* ditto for writes, these limits are SOFT! */ +/* + * Time after which to dispatch lower priority requests even if higher + * priority requests are pending. + */ +static const int prio_aging_expire = 10 * HZ; static const int writes_starved = 2; /* max times reads can starve a write */ static const int fifo_batch = 16; /* # of sequential requests treated as one by the above parameters. For throughput. */ @@ -96,6 +101,7 @@ struct deadline_data { int writes_starved; int front_merges; u32 async_depth; + int prio_aging_expire; spinlock_t lock; spinlock_t zone_lock; @@ -338,12 +344,27 @@ deadline_next_request(struct deadline_data *dd, struct dd_per_prio *per_prio, return rq; } +/* + * Returns true if and only if @rq started after @latest_start where + * @latest_start is in jiffies. + */ +static bool started_after(struct deadline_data *dd, struct request *rq, + unsigned long latest_start) +{ + unsigned long start_time = (unsigned long)rq->fifo_time; + + start_time -= dd->fifo_expire[rq_data_dir(rq)]; + + return time_after(start_time, latest_start); +} + /* * deadline_dispatch_requests selects the best request according to - * read/write expire, fifo_batch, etc + * read/write expire, fifo_batch, etc and with a start time <= @latest_start. */ static struct request *__dd_dispatch_request(struct deadline_data *dd, - struct dd_per_prio *per_prio) + struct dd_per_prio *per_prio, + unsigned long latest_start) { struct request *rq, *next_rq; enum dd_data_dir data_dir; @@ -355,6 +376,8 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd, if (!list_empty(&per_prio->dispatch)) { rq = list_first_entry(&per_prio->dispatch, struct request, queuelist); + if (started_after(dd, rq, latest_start)) + return NULL; list_del_init(&rq->queuelist); goto done; } @@ -432,6 +455,9 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd, dd->batching = 0; dispatch_request: + if (started_after(dd, rq, latest_start)) + return NULL; + /* * rq is the selected appropriate request. */ @@ -449,6 +475,34 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd, return rq; } +/* + * Check whether there are any requests with priority other than DD_RT_PRIO + * that were inserted more than prio_aging_expire jiffies ago. + */ +static struct request *dd_dispatch_prio_aged_requests(struct deadline_data *dd, + unsigned long now) +{ + struct request *rq; + enum dd_prio prio; + int prio_cnt; + + lockdep_assert_held(&dd->lock); + + prio_cnt = !!dd_queued(dd, DD_RT_PRIO) + !!dd_queued(dd, DD_BE_PRIO) + + !!dd_queued(dd, DD_IDLE_PRIO); + if (prio_cnt < 2) + return NULL; + + for (prio = DD_BE_PRIO; prio <= DD_PRIO_MAX; prio++) { + rq = __dd_dispatch_request(dd, &dd->per_prio[prio], + now - dd->prio_aging_expire); + if (rq) + return rq; + } + + return NULL; +} + /* * Called from blk_mq_run_hw_queue() -> __blk_mq_sched_dispatch_requests(). * @@ -460,15 +514,26 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd, static struct request *dd_dispatch_request(struct blk_mq_hw_ctx *hctx) { struct deadline_data *dd = hctx->queue->elevator->elevator_data; + const unsigned long now = jiffies; struct request *rq; enum dd_prio prio; spin_lock(&dd->lock); + rq = dd_dispatch_prio_aged_requests(dd, now); + if (rq) + goto unlock; + + /* + * Next, dispatch requests in priority order. Ignore lower priority + * requests if any higher priority requests are pending. + */ for (prio = 0; prio <= DD_PRIO_MAX; prio++) { - rq = __dd_dispatch_request(dd, &dd->per_prio[prio]); - if (rq) + rq = __dd_dispatch_request(dd, &dd->per_prio[prio], now); + if (rq || dd_queued(dd, prio)) break; } + +unlock: spin_unlock(&dd->lock); return rq; @@ -573,6 +638,7 @@ static int dd_init_sched(struct request_queue *q, struct elevator_type *e) dd->front_merges = 1; dd->last_dir = DD_WRITE; dd->fifo_batch = fifo_batch; + dd->prio_aging_expire = prio_aging_expire; spin_lock_init(&dd->lock); spin_lock_init(&dd->zone_lock); @@ -796,6 +862,7 @@ static ssize_t __FUNC(struct elevator_queue *e, char *page) \ #define SHOW_JIFFIES(__FUNC, __VAR) SHOW_INT(__FUNC, jiffies_to_msecs(__VAR)) SHOW_JIFFIES(deadline_read_expire_show, dd->fifo_expire[DD_READ]); SHOW_JIFFIES(deadline_write_expire_show, dd->fifo_expire[DD_WRITE]); +SHOW_JIFFIES(deadline_prio_aging_expire_show, dd->prio_aging_expire); SHOW_INT(deadline_writes_starved_show, dd->writes_starved); SHOW_INT(deadline_front_merges_show, dd->front_merges); SHOW_INT(deadline_async_depth_show, dd->front_merges); @@ -825,6 +892,7 @@ static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, msecs_to_jiffies) STORE_JIFFIES(deadline_read_expire_store, &dd->fifo_expire[DD_READ], 0, INT_MAX); STORE_JIFFIES(deadline_write_expire_store, &dd->fifo_expire[DD_WRITE], 0, INT_MAX); +STORE_JIFFIES(deadline_prio_aging_expire_store, &dd->prio_aging_expire, 0, INT_MAX); STORE_INT(deadline_writes_starved_store, &dd->writes_starved, INT_MIN, INT_MAX); STORE_INT(deadline_front_merges_store, &dd->front_merges, 0, 1); STORE_INT(deadline_async_depth_store, &dd->front_merges, 1, INT_MAX); @@ -843,6 +911,7 @@ static struct elv_fs_entry deadline_attrs[] = { DD_ATTR(front_merges), DD_ATTR(async_depth), DD_ATTR(fifo_batch), + DD_ATTR(prio_aging_expire), __ATTR_NULL };