linux-kernel - Re: [patch] Give kjournald a IOPRIO_CLASS

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Message-ID: <20071114171805.GA20959@elte.hu>
Date:	Wed, 14 Nov 2007 18:18:05 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	"Alan D. Brunelle" <Alan.Brunelle@...com>,
	Rik van Riel <riel@...hat.com>, arjan@...radead.org,
	jens.axboe@...cle.com, linux-kernel@...r.kernel.org
Subject: Re: [patch] Give kjournald a IOPRIO_CLASS_RT io priority


* Andrew Morton <akpm@...ux-foundation.org> wrote:

> ooh, more performance testing.  Thanks
> 
> >     * The overwriter task (on an 8GiB file), average over 10 runs:
> >           o 2.6.24 - 300.88226 seconds
> >           o 2.6.24 + Arjan's patch - 403.85505 seconds
> > 
> >     * The read-a-different-kernel-tree task, average over 10 runs:
> >           o 2.6.24 - 46.8145945549 seconds
> >           o 2.6.24 + Arjan's patch - 39.6430601119 seconds
> > 
> >     * The large-linear-read task (on an 8GiB file), average over 10 runs:
> >           o 2.6.24 - 290.32522 seconds
> >           o 2.6.24 + Arjan's patch - 386.34860 seconds
> 
> These are *large* differences, making this a very signifcant patch.  
> Much care is needed now.

and the numbers suggest it's mostly a severe performance regression. 
That's not what i have expected - ho hum. Apologies for my earlier 
"please merge it already!" whining.

	Ingo
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