linux-kernel - Re: [PATCH 00/14] introduce the BFQ-v0 I/O scheduler as an extra scheduler

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Message-ID: <20161026113443.GA13587@quack2.suse.cz>
Date:   Wed, 26 Oct 2016 13:34:43 +0200
From:   Jan Kara <jack@...e.cz>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     Paolo Valente <paolo.valente@...aro.org>,
        Jens Axboe <axboe@...nel.dk>, Tejun Heo <tj@...nel.org>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        ulf.hansson@...aro.org, linus.walleij@...aro.org,
        broonie@...nel.org, hare@...e.de, arnd@...db.de,
        bart.vanassche@...disk.com, grant.likely@...retlab.ca,
        jack@...e.cz, James.Bottomley@...senPartnership.com
Subject: Re: [PATCH 00/14] introduce the BFQ-v0 I/O scheduler as an extra
 scheduler

On Wed 26-10-16 03:19:03, Christoph Hellwig wrote:
> Just as last time:
> 
> big NAK for introducing giant new infrastructure like a new I/O scheduler
> for the legacy request structure.
> 
> Please direct your engergy towards blk-mq instead.

Christoph, we will probably talk about this next week but IMO rotating
disks and SATA based SSDs are going to stay with us for another 15 years,
likely more. For them blk-mq is no win, relatively complex IO scheduling
like CFQ or BFQ does is a big win for them in some cases. So I think IO
scheduling (and thus place for something like BFQ) is going to stay with us
for quite a long time still. So are we going to add hooks in blk-mq to
support full-blown IO scheduling at least for single queue devices? Or how
else do we want to support that HW?

								Honza
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR