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From "Bill Stoddard" <b...@wstoddard.com>
Subject RE: What is the source of this 'Thundering herd' redux?
Date Tue, 31 Dec 2002 18:56:46 GMT
I assume you are using the lastest version of 1.3.  Try experimenting with the
AcceptMutex config directive and see if selecting different values changes the
behaviour you are seeing.

Bill

> Hi,
>
> I have been trying to track down a nasty performance issue with apache
> 1.3 on linux 2.4.18 (RH7.2). I have narrowed the list down to two
> possible culprits (apache or the kernel). I use PHP as well, but I don't
> think that is responsible.
>
> The load spikes that occur look like all the processes are waking up
> (looking like the old 'thundering herd' problem). The odd thing is that
> just prior, no processes are running and the idle % soars.
>
> http://www.network54.com/spikes/vmstat.txt
>
> It appears that nothing can accept an incoming connection (maybe one
> process is supposed to, but does not) and so it then goes and wakes
> everyone up to get it handled.
>
> Any guess as to why (and where in the code) this happens?
>
> The kernel people say it is not their problem, that it is an apache
> issue.
>
> http://www.network54.com/spikes/
>


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