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From dlang <>
Subject [users@httpd] severe slowdowns under load with many virtualhosts
Date Thu, 26 Jun 2003 06:23:25 GMT
I have apache 2.0.45 running on AIX 4.3.3 on 4 processor RS/6000 servers
with 4G of ram. I host ~1500 websites with both http and https versions. I
have found that if I configure more then a few hundred virtual hosts in
one config (either as a single file or as includes) things seem fine when
I do stress tests against a single site (useing ab for example) but when
under a production load with people hitting many different sites the
machine slows to a crawl with all the CPU's pegged. if I reduce the config
down to 300-400 sites and expose it to the exact same load the problem
does not happen. when I say exact same load I mean not only the same
number of hits, but also hitting the same virtual hosts (the server only
has some of the IP addresses directed to it) I would very much like to be
able to increase the number of virtualhosts per config so that I can load
balance across multiple machines.

Feel free to ask for whatever additional info you need

apache is configured with the forking memory model (we have recompiled it
for threads and seen no benifit) and use the following modules (all
compiled in, this is a cut-and-paste from our discussion of which ones to
> > LoadModule access_module modules/
> > LoadModule include_module modules/
> > LoadModule deflate_module modules/
> > LoadModule log_config_module modules/
> > LoadModule env_module modules/
> > LoadModule setenvif_module modules/
> > LoadModule ssl_module modules/
> > LoadModule mime_module modules/
> > LoadModule status_module modules/
> > LoadModule cgi_module modules/
>  > LoadModule imap_module modules/
>  > LoadModule alias_module modules/
> > LoadModule auth_module modules/
> > LoadModule proxy_module modules/
> > LoadModule proxy_connect_module modules/
> > LoadModule proxy_http_module modules/
> > LoadModule rewrite_module modules/
> > LoadModule authenticache_module modules/

David Lang

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