--- On Fri, 10/17/08, Michael Peters wrote:
> To think about how this works under mod_perl, pretend that
> all of your scripts are put together into
> 1 larger script and all those "use" statements
> are repeated. Does having multiple "use CGI"
> statements make your script use more memory? No. CGI.pm is
> only loaded once.


Thanks for clarifying that. I was never sure if the libraries would be shared or placed in their own namespace somehow.


> Preloading helps with speed (you don't get the the
> initial loading hit for a module the first time
> it's used in a specific process) but it can also help
> with memory on certain OSs. For instance,
> Linux has Copy-On-Write memory so that if you preload
> modules it saves on actual physical RAM used
> (even though the separate processes think they have their
> own separate memory spaces).


I'm using linux 2.6.23 with Apache 2.2.8

I did not know about the copy-on-write memory. I've probably heard the term many times, but always assumed it was in regards to a filesystem. That can definitely reduce the memory -- I must move more common libraries to startup.pl


> This is one of the reasons that most people put a vanilla
> Apache (or something else like squid, lighttpd, varnish,
> etc) in front as a Proxy. When you do that,
> even if you're running both the proxy and the mod_perl
> server on the same physical machine you need
> a lot less RAM then if you just ran a mod_perl server
> trying to do static and dynamic requests.
>


Hmmmm. I'm still serving mod_perl programs and static pages from one Apache server, with average load of about 1 hit per second. It's worth looking into some of these combinations a little more.

Thanks for your great answers!
Tom

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