Re: strange high system cpu usage.

[Elliott Johnson]

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@xxxxxxxxxxxxx>
> To: linux-kernel@xxxxxxxxxxxxxxx
> 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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