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From Brian Pane <brian.p...@cnet.com>
Subject Re: 2.0.30-dev load spiking [was: upgrade to FreeBSD 4.5-PRERELEASE]
Date Wed, 02 Jan 2002 20:46:46 GMT
Greg Ames wrote:

>when I came in to work today, top on daedalus showed all three load
>averages above 27. vmstat -w 5 showed that the number of processes in
>the run queue was jumping up to over 350 fairly frequently, and there's
>some evidence of spikes in CPU usage.  So I bounced us back to httpd
>2_0_28, and the bad behavior has definately gotten better.
>
>Either we're doing something to make more processes run-able at times,
>or httpd related processes are staying in the run queue longer than they
>used to sometimes.  I think it's the latter.  For one thing, the idle
>CPU drops down to zero periodically, which I've never seen with 2_0_28.  
>
>Jeff & I discussed how to troubleshoot this baby.  Some thoughts:
>* compare trusses and look for abnormalities
>* scrutinize the error logs
>* calculate and log how much CPU time each request takes, the thought
>being that some requests are burning a lot more CPU than they used to.  
>
>Any other ideas?  
>

Do you have a way to take a snapshot of each httpd process's stack
backtrace?  On Solaris, I'd do this by running /usr/proc/bin/pstack
on each pid; I don't know if FreeBSD has a similar functionality.
This would give us a picture of what all those runnable processes
are doing.

--Brian




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