From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
Subject: Re: [PATCH RFC - TAKE TWO - 00/12] New version of the BFQ I/O
	Scheduler
Date: Wed, 4 Jun 2014 07:53:30 -0700
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To: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Jens Axboe <axboe-tSWWG44O7X1aa/9Udqfwiw@public.gmane.org>, Paolo Valente <paolo.valente-rcYM44yAMweonA0d6jMUrA@public.gmane.org>, containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, Fabio Checconi <fchecconi-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Arianna Avanzini <avanzini.arianna-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Paolo Valente <posta_paolo-whZMOeQn8C0@public.gmane.org>

On Wed, Jun 04, 2014 at 10:50:53AM -0400, Tejun Heo wrote:
> Hmmm... the biggest thing is ioscheds.  They heavily rely on being
> strongly synchronized and are pretty important for rotating rusts.
> Maybe they can be made to work with blk-mq by forcing single queue or
> something but do we wnat that?

Jens is planning to add an (optional) I/O scheduler to blk-mq, and
that is indeed required for proper disk support.  I don't think there
even is a need to limit it to a single queue technically, although
devices that support multiple queues are unlikely to need I/O
scheduling.