linux-kernel - Re: [2.6 patch] make I/O schedulers non-modular

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Date:	Mon, 26 Nov 2007 08:28:41 +0300
From:	Al Boldi <a1426z@...ab.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, Adrian Bunk <bunk@...sta.de>,
	Jens Axboe <jens.axboe@...cle.com>
Subject: Re: [2.6 patch] make I/O schedulers non-modular

Andrew Morton wrote:
> (cc's lovingly restored.  Please do not do that)

Thanks!  I'm replying off list.

> On Mon, 26 Nov 2007 07:57:00 +0300 Al Boldi <a1426z@...ab.com> wrote:
> > Jens Axboe wrote:
> > > On Sun, Nov 25 2007, Adrian Bunk wrote:
> > > > Is there any technical reason why we need 4 different schedulers at
> > > > all?
> > >
> > > Until we have the perfect scheduler :-)
> > >
> > > With some hard work and testing, we should be able to get rid of 'as'.
> > > It still beats cfq for some of the workloads that deadline is good at,
> > > so not quite yet.
> > >
> > > > I have the gut feeling that the usual thing happens and people e.g.
> > > > not report some cfq problems because as works for them...
> > >
> > > There's always a risk with "duplicate", like several drivers for the
> > > same hardware. I'm not disputing that.
> >
> > Actually, both 'cfq' and 'as' are broken, and have been repeatedly
> > reported as such.  Deadline is the only one that currently looks sane,
> > and seems like a good starting point for a more involved iosched.  But
> > keep in mind, the fact that 'cfq' and 'as' are broken may also point to
> > a lower-level block-io problem.  So, incrementally improving deadline
> > may help discovering the problems both 'cfq' and 'as' are plagued with.
>
> Sorry, but these are vague and unuseful assertions.
>
> Please send bug reports, preferably with testcases which developers can
> use when fixing the bugs.

http://bugzilla.kernel.org/show_bug.cgi?id=5900


Thanks again!

--
Al

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