Message-ID: <3C4852F9.C6797478@sap.com>
Date: Fri, 18 Jan 2002 17:53:13 +0100
From: Willi =?iso-8859-1?Q?N=FC=DFer?= <wilhelm.nuesser@sap.com>
Organization: SAP AG
MIME-Version: 1.0
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
CC: Andrea Arcangeli <andrea@suse.de>, linux-kernel@vger.kernel.org,
        Rik van Riel <riel@conectiva.com.br>
Subject: Re: clarification about redhat and vm
In-Reply-To: <E16RFE9-00042W-00@the-village.bc.nu>
Content-Type: text/plain; charset=us-ascii
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Sender: linux-kernel-owner@vger.kernel.org

Alan Cox wrote:
> 
> > "If redhat doesn't use the -aa VM " was a short form of "if redhat
> > cannot see the goodness of all the bugfixing work that happened between
> > the 2.4.9 VM and any current branch 2.4, and so if they keep shipping
> > 2.4.9 VM as the best one for DBMS and critical VM apps like the SAP
> > benchmark".
> 
> The RH VM is totally unrelated to the crap in 2.4.9 vanilla. The SAP comment
> begs a question. 2.4.10 seems to have problems remembering to actually
> do fsync()'s. How much of your SAP benchmark is from fsync's that dont
> happen ? Do you get the same values with 2.4.18-aa ?


Well, basically we checked the thing many times with quite different
kernels.
Our current tests - which show exactly the same results as
2.4.[10,14,15] - run
on the new "official" SuSE kernel 2.4.16.  Again, we  observe a
performance increase
in high swap situations of about a factor of ten compared to 2.4.[7,9].
 
IMO, this shows that errors like fsync etc. are _not_ responsible for
the improved
performance.  

But of course, we will check the newer kernels as well.  I think we
could live 
with another factor of ten ...


-- 
Best regards
Willi

-----------------------------------
Willi Nuesser
SAP Linuxlab
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