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author | Bart Van Assche <bvanassche@acm.org> | 2021-09-27 15:03:28 -0700 |
---|---|---|
committer | Jens Axboe <axboe@kernel.dk> | 2021-10-18 06:17:02 -0600 |
commit | 322cff70d46c6c230a722684fd65ae6b5f57436e (patch) | |
tree | 14e1cec4c3b0e0f5815212019c3a26937dcfdd5c /block/mq-deadline.c | |
parent | bce0363ed84af8e8e27df464b2082f4b5f58b57e (diff) | |
download | linux-322cff70d46c6c230a722684fd65ae6b5f57436e.tar.bz2 |
block/mq-deadline: Prioritize high-priority requests
In addition to reverting commit 7b05bf771084 ("Revert "block/mq-deadline:
Prioritize high-priority requests""), this patch uses 'jiffies' instead
of ktime_get() in the code for aging lower priority requests.
This patch has been tested as follows:
Measured QD=1/jobs=1 IOPS for nullb with the mq-deadline scheduler.
Result without and with this patch: 555 K IOPS.
Measured QD=1/jobs=8 IOPS for nullb with the mq-deadline scheduler.
Result without and with this patch: about 380 K IOPS.
Ran the following script:
set -e
scriptdir=$(dirname "$0")
if [ -e /sys/module/scsi_debug ]; then modprobe -r scsi_debug; fi
modprobe scsi_debug ndelay=1000000 max_queue=16
sd=''
while [ -z "$sd" ]; do
sd=$(basename /sys/bus/pseudo/drivers/scsi_debug/adapter*/host*/target*/*/block/*)
done
echo $((100*1000)) > "/sys/block/$sd/queue/iosched/prio_aging_expire"
if [ -e /sys/fs/cgroup/io.prio.class ]; then
cd /sys/fs/cgroup
echo restrict-to-be >io.prio.class
echo +io > cgroup.subtree_control
else
cd /sys/fs/cgroup/blkio/
echo restrict-to-be >blkio.prio.class
fi
echo $$ >cgroup.procs
mkdir -p hipri
cd hipri
if [ -e io.prio.class ]; then
echo none-to-rt >io.prio.class
else
echo none-to-rt >blkio.prio.class
fi
{ "${scriptdir}/max-iops" -a1 -d32 -j1 -e mq-deadline "/dev/$sd" >& ~/low-pri.txt & }
echo $$ >cgroup.procs
"${scriptdir}/max-iops" -a1 -d32 -j1 -e mq-deadline "/dev/$sd" >& ~/hi-pri.txt
Result:
* 11000 IOPS for the high-priority job
* 40 IOPS for the low-priority job
If the prio 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: Niklas Cassel <Niklas.Cassel@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Link: https://lore.kernel.org/r/20210927220328.1410161-5-bvanassche@acm.org
[axboe: @latest -> @latest_start]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/mq-deadline.c')
-rw-r--r-- | block/mq-deadline.c | 77 |
1 files changed, 73 insertions, 4 deletions
diff --git a/block/mq-deadline.c b/block/mq-deadline.c index b262f40f32c0..2001ac186f5c 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; @@ -339,11 +345,26 @@ deadline_next_request(struct deadline_data *dd, struct dd_per_prio *per_prio, } /* + * 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 @@ dispatch_find_request: dd->batching = 0; dispatch_request: + if (started_after(dd, rq, latest_start)) + return NULL; + /* * rq is the selected appropriate request. */ @@ -450,6 +476,34 @@ done: } /* + * 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(). * * One confusing aspect here is that we get called for a specific @@ -460,15 +514,26 @@ done: 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 }; |