linux-kernel - Re: scsi-mq

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Date:	Fri, 13 Jun 2014 08:42:57 +0200
From:	Bart Van Assche <bvanassche@....org>
To:	Christoph Hellwig <hch@....de>,
	James Bottomley <James.Bottomley@...senPartnership.com>
CC:	Jens Axboe <axboe@...nel.dk>, Robert Elliot <Elliott@...com>,
	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: scsi-mq

On 06/12/14 15:48, Christoph Hellwig wrote:
> The usage of blk-mq dramatically decreases CPU usage under all workloads going
> down from 100% CPU usage that the old setup can hit easily to usually less
> than 20% for maxing out storage subsystems with 512 byte reads and writes,
> and it allows to easily achieve millions of IOPS. Bart and Robert have
> helped with some very detailed measurements that they might be able to send
> in reply to this, although these usually involve significantly reworked low
> level drivers to avoid other bottle necks.

Thanks Christoph for writing up this excellent summary. In case anyone
is wondering which LLD changes Christoph is referring to: the tests I
ran myself were with an SRP initiator driver modified to use multiple
RDMA channels between initiator and target instead of a single channel.
I will post these changes for review on the linux-rdma mailing list as
soon as I have the time.

Bart.

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