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From David Hodgkinson <da...@hodgkinson.org>
Subject Re: mod_perl performance question
Date Fri, 09 Apr 2004 17:36:10 GMT

On 8 Apr 2004, at 16:48, Pascal Felber wrote:

> We have noticed some "strange" behavior when stress-testing one of our
> perl modules and we haven't managed to find an explanation or 
> workaround
> in the mod_perl documentation. We have reproduced this problem with a
> minimal module, installed as a PerlResponseHandler, that simply sends 
> am
> HTTP 302 redirection message to the client. The server is a P4@1.5GHz
> 512MB, running linux 2.4.18-3, Apache 2.0.48, and mod_perl 1.99_08. We
> have run benchmarks using the `siege' application with an increasing
> number of clients and we have measured the latency of every request.
>
> I have put a graph online at http://www.eurecom.fr/~felber/mod_perl.gif
> that illustrates the problem. The response time of the server is 
> roughly
> constant but we observe some pretty high spikes in the latency every 30
> seconds or so, as if the server was interrupted for a short period of
> time (approx. 300 ms). The delay of 300 ms seems very high for tasks
> like shared memory accesses or garbage collection, given that our test
> module does almost nothing. When running the same test using mod_alias
> for redirections, there are no such spikes; so it really looks like 
> they
> are due to mod_perl rather than the OS, Apache, or the network. There
> might be an obvious explanation but we have limited expertise with
> mod_perl and we would very much appreciate some help from other users 
> on
> this list.

What else is running on the machine? what does vmstat show?


-- 
Dave Hodgkinson
CTO, Rockit Factory Ltd.
http://www.rockitfactory.com/
Web sites for rock bands


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