linux-kernel - Re: strange high system cpu usage.

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Message-Id: <20070331020837.C597743FCD@ws5-1.us4.outblaze.com>
Date:	Sat, 31 Mar 2007 10:08:37 +0800
From:	"Elliott Johnson" <ejohnson@...uxmail.org>
To:	"Elliott Johnson" <ejohnson@...uxmail.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: strange high system cpu usage.

Lee

Thanks for your help.  In testing different kernels we found that using an unpatched kernel from kernel.org seems to fix the problem.  I'm assuming that a patch added in the gentoo-sources patch set was creating the problem.  Our once 8 minute untar is now down to 7-8 seconds with a vanilla 2.6.18.6 kernel.

If anyone is interested in our oprofile code or other info, just ask and I'll post it.  Otherwise I'll be reporting this to the gentoo developers.

-E

> ----- Original Message -----
> From: "Elliott Johnson" <ejohnson@...uxmail.org>
> To: linux-kernel@...r.kernel.org
> Subject: Re: strange high system cpu usage.
> Date: 	Fri, 30 Mar 2007 11:54:57 +0800
> 
> 
> > What problem are you trying to solve?  IOW, how do you know it's not
> > just an artifact of diferent load average calculation between 2.4 and
> > 2.6?
> >
> > Are you actually seeing reduced throughput/performance?  Or are you
> > just looking at load average?
> >
> > Lee
> 
> Well the problem is apparent, we are having abnormally high cpu 
> usage.  It's about a
> 20-40% performance hit.
> 
> The load calculations were not between 2.4 and 2.6 kernel versions, 
> but between 2.6.8 and
> 2.6.19.  Sorry if this wasn't very clear from my last email.
> 
> In trying to diagnose the problem I also looked at memory stats 
> (vmstat) and found the
> 'buffered' memory statistic way off from the comparable debian 
> (2.6.8) install (0-300kb
> versus 500mb).
> 
> The vmstat man page has little information on this statistic and 
> there seems to be varying
> explanations on the web.  I was hoping for a decisive explanation 
> (or link) and possibly
> advice in toggling this value (or reasons not to).
> 
> I'm still trying to work on this at my end.  Some recent tests show 
> that it might be
> related to the megasas driver or the large number of small files we 
> are using on a xfs
> formated 10T array.  I'll keep at it.
> 
> Thanks for your response,
> 
> -Elliott
> 
> =
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