From: Bart Van Assche <bart.vanassche@wdc.com>
To: Ming Lei <ming.lei@redhat.com>,
"linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>
Cc: Jens Axboe <axboe@fb.com>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
Omar Sandoval <osandov@fb.com>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
James Bottomley <james.bottomley@hansenpartnership.com>,
Christoph Hellwig <hch@lst.de>,
Don Brace <don.brace@microsemi.com>,
Kashyap Desai <kashyap.desai@broadcom.com>,
Mike Snitzer <snitzer@redhat.com>, Hannes Reinecke <hare@suse.de>,
Laurence Oberman <loberman@redhat.com>
Subject: Re: [PATCH V2 2/2] scsi: avoid to hold host-wide counter of host_busy for scsi_mq
Date: Mon, 25 Jun 2018 08:38:08 -0700 [thread overview]
Message-ID: <27a6f54a-49b5-460f-08fb-c7b9d2dc52ef@wdc.com> (raw)
In-Reply-To: <20180624140327.28146-3-ming.lei@redhat.com>
On 06/24/18 07:04, Ming Lei wrote:
> It isn't necessary to check the host depth in scsi_queue_rq() any more
> since it has been respected by blk-mq before calling scsi_queue_rq() via
> getting driver tag.
>
> Lots of LUNs may attach to same host, and per-host IOPS may reach millions
> level, so we should avoid to this expensive atomic operations on the
> hostwide counter in IO path.
>
> This patch implemens scsi_host_busy() via blk_mq_tagset_busy_iter() for
> reading the count of busy IOs for scsi_mq.
>
> It is observed that IOPS is increased by 15% in IO test on scsi_debug
> (32 LUNs, 32 submit queues, 1024 can_queue, libaio/dio) in one
> dual-socket system.
Reviewed-by: Bart Van Assche <bart.vanassche@wdc.com>
next prev parent reply other threads:[~2018-06-25 15:38 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-24 14:03 [PATCH V2 0/2] scsi: scsi-mq: don't hold host_busy in IO path Ming Lei
2018-06-24 14:03 ` [PATCH V2 1/2] scsi: read host_busy via scsi_host_busy() Ming Lei
2018-06-25 15:37 ` Bart Van Assche
2018-06-24 14:03 ` [PATCH V2 2/2] scsi: avoid to hold host-wide counter of host_busy for scsi_mq Ming Lei
2018-06-25 15:38 ` Bart Van Assche [this message]
2018-06-29 16:20 ` [V2, " Guenter Roeck
2018-06-30 1:12 ` Ming Lei
2018-06-30 1:30 ` Ming Lei
2018-06-30 1:41 ` Guenter Roeck
2018-06-26 16:53 ` [PATCH V2 0/2] scsi: scsi-mq: don't hold host_busy in IO path Martin K. Petersen
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