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ANDROID: block: Improve shared tag set performance

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Remove the code for fair tag sharing because it significantly hurts
performance for UFS devices. Removing this code is safe because the
legacy block layer worked fine without any equivalent fairness
algorithm.

This algorithm hurts performance for UFS devices because UFS devices
have multiple logical units. One of these logical units (WLUN) is used
to submit control commands, e.g. START STOP UNIT. If any request is
submitted to the WLUN, the queue depth is reduced from 31 to 15 or
lower for data LUNs.

See also https://lore.kernel.org/linux-scsi/20221229030645.11558-1-ed.tsai@mediatek.com/

Cc: Christoph Hellwig <hch@lst.de>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Keith Busch <kbusch@kernel.org>
Cc: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Cc: Ed Tsai <ed.tsai@mediatek.com>
Change-Id: Ia6d75917d533f32fffc68348b52fd3d972c9074c
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Bug: 281845090
Bug: 307790116
Bug: 390523143
Link: https://lore.kernel.org/linux-block/20230103195337.158625-1-bvanassche@acm.org/
Signed-off-by: Bart Van Assche <bvanassche@google.com>
(cherry picked from commit 12a703a56f1b01d295a7ee92e931daa56727620f)
This commit is contained in:
Bart Van Assche
2023-05-10 09:32:41 -07:00
committed by Treehugger Robot
parent bc75210c05
commit f95c93db8b
3 changed files with 0 additions and 46 deletions
Download Patch File Download Diff File Expand all files Collapse all files
block/blk-mq-tag.c
-4
View File
@@ -106,10 +106,6 @@ void __blk_mq_tag_idle(struct blk_mq_hw_ctx *hctx)
static int __blk_mq_get_tag(struct blk_mq_alloc_data *data,
struct sbitmap_queue *bt)
{
if (!data->q->elevator && !(data->flags & BLK_MQ_REQ_RESERVED) &&
!hctx_may_queue(data->hctx, bt))
return BLK_MQ_NO_TAG;
if (data->shallow_depth)
return sbitmap_queue_get_shallow(bt, data->shallow_depth);
else
block/blk-mq.c
-3
View File
@@ -1837,9 +1837,6 @@ bool __blk_mq_alloc_driver_tag(struct request *rq)
if (blk_mq_tag_is_reserved(rq->mq_hctx->sched_tags, rq->internal_tag)) {
bt = &rq->mq_hctx->tags->breserved_tags;
tag_offset = 0;
} else {
if (!hctx_may_queue(rq->mq_hctx, bt))
return false;
}
tag = __sbitmap_queue_get(bt);
block/blk-mq.h
-39
View File
@@ -391,45 +391,6 @@ static inline void blk_mq_free_requests(struct list_head *list)
}
}
/*
* For shared tag users, we track the number of currently active users
* and attempt to provide a fair share of the tag depth for each of them.
*/
static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
struct sbitmap_queue *bt)
{
unsigned int depth, users;
if (!hctx || !(hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED))
return true;
/*
* Don't try dividing an ant
*/
if (bt->sb.depth == 1)
return true;
if (blk_mq_is_shared_tags(hctx->flags)) {
struct request_queue *q = hctx->queue;
if (!test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
return true;
} else {
if (!test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
return true;
}
users = READ_ONCE(hctx->tags->active_queues);
if (!users)
return true;
/*
* Allow at least some tags
*/
depth = max((bt->sb.depth + users - 1) / users, 4U);
return __blk_mq_active_requests(hctx) < depth;
}
/* run the code block in @dispatch_ops with rcu/srcu read lock held */
#define __blk_mq_run_dispatch_ops(q, check_sleep, dispatch_ops) \
do { \