Date: Fri, 19 Mar 2004 12:23:10 +0100
Message-ID: <s5hu10laxnl.wl@alsa2.suse.de>
From: Takashi Iwai <tiwai@suse.de>
To: Eric St-Laurent <ericstl34@sympatico.ca>
Cc: Chris Mason <mason@suse.com>, Andrew Morton <akpm@osdl.org>,
       linux-kernel@vger.kernel.org
Subject: Re: CONFIG_PREEMPT and server workloads
In-Reply-To: <1079665660.7609.6.camel@orbiter>
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	<20040318060358.GC29530@dualathlon.random>
	<s5hlllycgz3.wl@alsa2.suse.de>
	<1079665660.7609.6.camel@orbiter>
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At Thu, 18 Mar 2004 22:07:41 -0500,
Eric St-Laurent wrote:
> 
> On Thu, 2004-03-18 at 10:28, Takashi Iwai wrote:
> 
> > in my case with reiserfs, i got 0.4ms RT-latency with my test suite
> > (with athlon 2200+).
> > 
> > there is another point to be fixed in the reiserfs journal
> > transaction.  then you'll get 0.1ms RT-latency without preemption.
> 
> Are you talking about the following patch recently merged in Linus tree?
> 
> [PATCH] resierfs: scheduling latency improvements
> http://linus.bkbits.net:8080/linux-2.5/cset@40571b49jtE7PzOtsXjBx65-GoDijg

i've tested the suse kernel, so the patch above was already in it.
i'm not sure whether mm tree already includes the all relevant
fixes... Chris?

what i wrote above about is loops in do_journal_end().  but i can't
tell you surely unless i test the mm kernel again.

> I'm interested to try any patch you might have to help reduce latency
> with reiserfs.

AFAIK, even only the fix of mpage_writepages() will reduce the latency
very much.  please give a try.


Takashi
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