From: Bart Van Assche <bvanassche@acm.org> To: Jens Axboe <axboe@kernel.dk> Cc: linux-block@vger.kernel.org, Christoph Hellwig <hch@lst.de>, Jaegeuk Kim <jaegeuk@kernel.org>, Bart Van Assche <bvanassche@acm.org>, Damien Le Moal <damien.lemoal@wdc.com>, Hannes Reinecke <hare@suse.de>, Ming Lei <ming.lei@redhat.com>, Johannes Thumshirn <johannes.thumshirn@wdc.com>, Himanshu Madhani <himanshu.madhani@oracle.com> Subject: [PATCH 14/14] block/mq-deadline: Prioritize high-priority requests Date: Tue, 8 Jun 2021 16:07:03 -0700 [thread overview] Message-ID: <20210608230703.19510-15-bvanassche@acm.org> (raw) In-Reply-To: <20210608230703.19510-1-bvanassche@acm.org> While one or more requests with a certain I/O priority are pending, do not dispatch lower priority requests. Dispatch lower priority requests anyway after the "aging" time has expired. This patch has been tested as follows: modprobe scsi_debug ndelay=1000000 max_queue=16 && sd='' && while [ -z "$sd" ]; do sd=/dev/$(basename /sys/bus/pseudo/drivers/scsi_debug/adapter*/host*/target*/*/block/*) done && echo $((100*1000)) > /sys/block/$sd/queue/iosched/aging_expire && cd /sys/fs/cgroup/blkio/ && echo $$ >cgroup.procs && echo 2 >blkio.prio.class && mkdir -p hipri && cd hipri && echo 1 >blkio.prio.class && { max-iops -a1 -d32 -j1 -e mq-deadline $sd >& ~/low-pri.txt & } && echo $$ >cgroup.procs && max-iops -a1 -d32 -j1 -e mq-deadline $sd >& ~/hi-pri.txt Result: * 11000 IOPS for the high-priority job * 400 IOPS for the low-priority job If the aging expiry time is changed from 100s into 0, the IOPS results change into 6712 and 6796 IOPS. The max-iops script is a script that runs fio with the following arguments: --bs=4K --gtod_reduce=1 --ioengine=libaio --ioscheduler=${arg_e} --runtime=60 --norandommap --rw=read --thread --buffered=0 --numjobs=${arg_j} --iodepth=${arg_d} --iodepth_batch_submit=${arg_a} --iodepth_batch_complete=$((arg_d / 2)) --name=${positional_argument_1} --filename=${positional_argument_1} Cc: Damien Le Moal <damien.lemoal@wdc.com> Cc: Hannes Reinecke <hare@suse.de> Cc: Christoph Hellwig <hch@lst.de> Cc: Ming Lei <ming.lei@redhat.com> Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com> Cc: Himanshu Madhani <himanshu.madhani@oracle.com> Signed-off-by: Bart Van Assche <bvanassche@acm.org> --- block/mq-deadline-main.c | 42 +++++++++++++++++++++++++++++++++++----- 1 file changed, 37 insertions(+), 5 deletions(-) diff --git a/block/mq-deadline-main.c b/block/mq-deadline-main.c index 1b2b6c1de5b8..cecdb475a610 100644 --- a/block/mq-deadline-main.c +++ b/block/mq-deadline-main.c @@ -32,6 +32,11 @@ */ 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 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. */ @@ -90,6 +95,7 @@ struct deadline_data { int writes_starved; int front_merges; u32 async_depth; + int aging_expire; spinlock_t lock; spinlock_t zone_lock; @@ -363,10 +369,10 @@ deadline_next_request(struct deadline_data *dd, enum dd_prio prio, /* * 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. */ static struct request *__dd_dispatch_request(struct deadline_data *dd, - enum dd_prio prio) + enum dd_prio prio, u64 latest_start_ns) { struct request *rq, *next_rq; enum dd_data_dir data_dir; @@ -378,6 +384,8 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd, if (!list_empty(&dd->dispatch[prio])) { rq = list_first_entry(&dd->dispatch[prio], struct request, queuelist); + if (rq->start_time_ns > latest_start_ns) + return NULL; list_del_init(&rq->queuelist); goto done; } @@ -457,6 +465,8 @@ static struct request *__dd_dispatch_request(struct deadline_data *dd, dd->batching = 0; dispatch_request: + if (rq->start_time_ns > latest_start_ns) + return NULL; /* * rq is the selected appropriate request. */ @@ -493,15 +503,32 @@ 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; - struct request *rq; + const u64 now_ns = ktime_get_ns(); + struct request *rq = NULL; enum dd_prio prio; spin_lock(&dd->lock); - for (prio = 0; prio <= DD_PRIO_MAX; prio++) { - rq = __dd_dispatch_request(dd, prio); + /* + * Start with dispatching requests whose deadline expired more than + * aging_expire jiffies ago. + */ + for (prio = DD_BE_PRIO; prio <= DD_PRIO_MAX; prio++) { + rq = __dd_dispatch_request(dd, prio, now_ns - + jiffies_to_nsecs(dd->aging_expire)); 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, prio, now_ns); + if (rq || dd_queued(dd, prio)) break; } + +unlock: spin_unlock(&dd->lock); return rq; @@ -607,6 +634,7 @@ static int dd_init_sched(struct request_queue *q, struct elevator_type *e) dd->writes_starved = writes_starved; dd->front_merges = 1; dd->fifo_batch = fifo_batch; + dd->aging_expire = aging_expire; spin_lock_init(&dd->lock); spin_lock_init(&dd->zone_lock); @@ -725,6 +753,7 @@ static void dd_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq, trace_block_rq_insert(rq); if (at_head) { + rq->fifo_time = jiffies; list_add(&rq->queuelist, &dd->dispatch[prio]); } else { deadline_add_rq_rb(dd, rq); @@ -841,6 +870,7 @@ 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_aging_expire_show, dd->aging_expire); SHOW_INT(deadline_writes_starved_show, dd->writes_starved); SHOW_INT(deadline_front_merges_show, dd->front_merges); SHOW_INT(deadline_fifo_batch_show, dd->fifo_batch); @@ -869,6 +899,7 @@ 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_aging_expire_store, &dd->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_fifo_batch_store, &dd->fifo_batch, 0, INT_MAX); @@ -885,6 +916,7 @@ static struct elv_fs_entry deadline_attrs[] = { DD_ATTR(writes_starved), DD_ATTR(front_merges), DD_ATTR(fifo_batch), + DD_ATTR(aging_expire), __ATTR_NULL };
next prev parent reply other threads:[~2021-06-08 23:07 UTC|newest] Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-06-08 23:06 [PATCH 00/14] Improve I/O priority support Bart Van Assche 2021-06-08 23:06 ` [PATCH 01/14] block/Kconfig: Make the BLK_WBT and BLK_WBT_MQ entries consecutive Bart Van Assche 2021-06-09 4:14 ` Damien Le Moal 2021-06-09 7:03 ` Johannes Thumshirn 2021-06-10 6:02 ` Hannes Reinecke 2021-06-08 23:06 ` [PATCH 02/14] block/blk-cgroup: Swap the blk_throtl_init() and blk_iolatency_init() calls Bart Van Assche 2021-06-09 4:19 ` Damien Le Moal 2021-06-09 7:05 ` Johannes Thumshirn 2021-06-10 6:02 ` Hannes Reinecke 2021-06-08 23:06 ` [PATCH 03/14] block/blk-rq-qos: Move a function from a header file into a C file Bart Van Assche 2021-06-09 4:22 ` Damien Le Moal 2021-06-10 6:03 ` Hannes Reinecke 2021-06-08 23:06 ` [PATCH 04/14] block: Introduce the ioprio rq-qos policy Bart Van Assche 2021-06-09 4:40 ` Damien Le Moal 2021-06-09 16:48 ` Bart Van Assche 2021-06-10 0:29 ` Damien Le Moal 2021-06-10 6:20 ` Hannes Reinecke 2021-06-10 17:14 ` Bart Van Assche 2021-06-08 23:06 ` [PATCH 05/14] block/mq-deadline: Add several comments Bart Van Assche 2021-06-10 6:21 ` Hannes Reinecke 2021-06-08 23:06 ` [PATCH 06/14] block/mq-deadline: Add two lockdep_assert_held() statements Bart Van Assche 2021-06-10 6:21 ` Hannes Reinecke 2021-06-08 23:06 ` [PATCH 07/14] block/mq-deadline: Remove two local variables Bart Van Assche 2021-06-10 6:22 ` Hannes Reinecke 2021-06-08 23:06 ` [PATCH 08/14] block/mq-deadline: Rename dd_init_queue() and dd_exit_queue() Bart Van Assche 2021-06-08 23:06 ` [PATCH 09/14] block/mq-deadline: Improve compile-time argument checking Bart Van Assche 2021-06-08 23:06 ` [PATCH 10/14] block/mq-deadline: Improve the sysfs show and store macros Bart Van Assche 2021-06-09 4:46 ` Damien Le Moal 2021-06-09 16:54 ` Bart Van Assche 2021-06-10 0:31 ` Damien Le Moal 2021-06-09 7:11 ` Johannes Thumshirn 2021-06-09 16:59 ` Bart Van Assche 2021-06-10 6:23 ` Hannes Reinecke 2021-06-08 23:07 ` [PATCH 11/14] block/mq-deadline: Reserve 25% of scheduler tags for synchronous requests Bart Van Assche 2021-06-10 6:26 ` Hannes Reinecke 2021-06-08 23:07 ` [PATCH 12/14] block/mq-deadline: Add I/O priority support Bart Van Assche 2021-06-09 5:03 ` Damien Le Moal 2021-06-09 17:25 ` Bart Van Assche 2021-06-10 0:39 ` Damien Le Moal 2021-06-10 6:35 ` Hannes Reinecke 2021-06-08 23:07 ` [PATCH 13/14] block/mq-deadline: Add cgroup support Bart Van Assche 2021-06-10 6:37 ` Hannes Reinecke 2021-06-08 23:07 ` Bart Van Assche [this message] 2021-06-09 5:10 ` [PATCH 14/14] block/mq-deadline: Prioritize high-priority requests Damien Le Moal 2021-06-10 6:43 ` Hannes Reinecke
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