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FROMLIST: block/mq-deadline: Only use zone locking if necessary

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Measurements have shown that limiting the queue depth to one per zone for
zoned writes has a significant negative performance impact on zoned UFS
devices. Hence this patch that disables zone locking by the mq-deadline
scheduler if the storage controller preserves the command order. This
patch is based on the following assumptions:
- It happens infrequently that zoned write requests are reordered by the
  block layer.
- The I/O priority of all write requests is the same per zone.
- Either no I/O scheduler is used or an I/O scheduler is used that
  serializes write requests per zone.

Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Ming Lei <ming.lei@redhat.com>
Change-Id: I2000beaa430f29ea1096149a7d3b8a5423b679ec
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Bug: 234829282
Link: https://lore.kernel.org/linux-block/20230804154821.3232094-1-bvanassche@acm.org/T/#made79fdd0e1d8d466f734250f3868b4d6f8105db
Signed-off-by: Bart Van Assche <bvanassche@google.com>
This commit is contained in:
Bart Van Assche
2023-01-09 15:27:34 -08:00
committed by Bart Van Assche
parent 5414ea3f50
commit 4e1d1b839d
1 changed files with 18 additions and 6 deletions
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24
block/mq-deadline.c
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@@ -340,6 +340,16 @@ static struct request *deadline_skip_seq_writes(struct deadline_data *dd,
return rq;
}
/*
* Use write locking if either QUEUE_FLAG_NO_ZONE_WRITE_LOCK has not been set.
* Not using zone write locking is only safe if the block driver preserves the
* request order.
*/
static bool dd_use_zone_write_locking(struct request_queue *q)
{
return blk_queue_is_zoned(q) && !blk_queue_no_zone_write_lock(q);
}
/*
* For the specified data direction, return the next request to
* dispatch using arrival ordered lists.
@@ -355,7 +365,7 @@ deadline_fifo_request(struct deadline_data *dd, struct dd_per_prio *per_prio,
return NULL;
rq = rq_entry_fifo(per_prio->fifo_list[data_dir].next);
if (data_dir == DD_READ || !blk_queue_is_zoned(rq->q))
if (data_dir == DD_READ || !dd_use_zone_write_locking(rq->q))
return rq;
/*
@@ -400,7 +410,7 @@ deadline_next_request(struct deadline_data *dd, struct dd_per_prio *per_prio,
if (!rq)
return NULL;
if (data_dir == DD_READ || !blk_queue_is_zoned(rq->q))
if (data_dir == DD_READ || !dd_use_zone_write_locking(rq->q))
return rq;
/*
@@ -528,8 +538,9 @@ dispatch_find_request:
}
/*
* For a zoned block device, if we only have writes queued and none of
* them can be dispatched, rq will be NULL.
* For a zoned block device that requires write serialization, if we
* only have writes queued and none of them can be dispatched, rq will
* be NULL.
*/
if (!rq)
return NULL;
@@ -554,7 +565,8 @@ done:
/*
* If the request needs its target zone locked, do it.
*/
blk_req_zone_write_lock(rq);
if (dd_use_zone_write_locking(rq->q))
blk_req_zone_write_lock(rq);
rq->rq_flags |= RQF_STARTED;
return rq;
}
@@ -931,7 +943,7 @@ static void dd_finish_request(struct request *rq)
atomic_inc(&per_prio->stats.completed);
if (blk_queue_is_zoned(q)) {
if (dd_use_zone_write_locking(rq->q)) {
unsigned long flags;
spin_lock_irqsave(&dd->zone_lock, flags);