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From: Jens Axboe <jens.axboe@oracle.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Paul Clements <paul.clements@steeleye.com>,
	randy.dunlap@oracle.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/1] NBD: make nbd default to deadline I/O scheduler
Date: Tue, 19 Feb 2008 11:05:36 +0100	[thread overview]
Message-ID: <20080219100536.GW23197@kernel.dk> (raw)
In-Reply-To: <20080219020204.2d448269.akpm@linux-foundation.org>

On Tue, Feb 19 2008, Andrew Morton wrote:
> On Tue, 19 Feb 2008 10:24:28 +0100 Jens Axboe <jens.axboe@oracle.com> wrote:
> 
> > On Tue, Feb 19 2008, Jens Axboe wrote:
> > > On Mon, Feb 18 2008, Andrew Morton wrote:
> > > > > +
> > > > >  	if (e && !try_module_get(e->elevator_owner))
> > > > >  		e = NULL;
> > > > 
> > > > Looks nice and simple.  There might be some of the usual ordering problems
> > > > when this is called during boot, maybe is-initramfs-available-yet problems,
> > > > etc.  But it's unlikely to make things regress from where they are now.
> > > 
> > > Isn't request_module() and below robust enough to handle that?
> > 
> > BTW, I've verified that it works as expected (at least after boot):
> > 
> > carl:/sys/block/sda/queue # cat scheduler 
> > noop [cfq] 
> > carl:/sys/block/sda/queue # echo anticipatory > scheduler 
> > carl:/sys/block/sda/queue # dmesg
> > [...]
> > io scheduler anticipatory registered
> > carl:/sys/block/sda/queue # cat scheduler 
> > noop cfq [anticipatory] 
> > 
> > So it properly loads as-iosched instead of failing, like it would have
> > done before and required the user to do a modprobe as-iosched first.
> > 
> > carl:/sys/block/sda/queue # echo foobar > scheduler 
> > -bash: echo: write error: Invalid argument
> > carl:/sys/block/sda/queue # dmesg
> > [...]
> > elevator: type foobar not found
> 
> Looks promising - let's run with it.  If there _are_ startup ordering
> problems then we won't be any worse off than we are now.

I've merged it for inclusion, since it tests fine here.

> otoh, the system must have _some_ io scheduler installed when talking to
> disks, so perhaps there won't be any such problems at all.

We are guarenteed to always have noop available, since you cannot
de-select that.

-- 
Jens Axboe


  reply	other threads:[~2008-02-19 10:05 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-08 16:47 Paul Clements
2008-02-08 17:33 ` Randy Dunlap
2008-02-08 18:11   ` Andrew Morton
2008-02-08 18:41     ` Paul Clements
2008-02-08 20:45       ` Jens Axboe
2008-02-08 20:47         ` Jens Axboe
2008-02-08 21:23           ` Paul Clements
2008-02-08 22:02             ` Andrew Morton
2008-02-09 13:30               ` Paul Clements
2008-02-12 23:16                 ` Andrew Morton
2008-02-18 18:16                   ` Jens Axboe
2008-02-18 23:50                     ` Andrew Morton
2008-02-19  9:19                       ` Jens Axboe
2008-02-19  9:24                         ` Jens Axboe
2008-02-19 10:02                           ` Andrew Morton
2008-02-19 10:05                             ` Jens Axboe [this message]
2008-02-08 22:45       ` [Nbd] " Mike Snitzer

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