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From "Paul J. Reder" <>
Subject Re: mod_include performance numbers
Date Fri, 20 Apr 2001 22:26:17 GMT
Marc Slemko wrote:
> On Fri, 20 Apr 2001, Paul J. Reder wrote:
> > Ian Holsman wrote:
> > > I'm not sure if this means that ALL filters are slow, or if
> > > it is just mod-include.
> >
> > I'm sure that there are some aspects of mod_include that can be improved,
> > but the fact of the matter is that a filter that looks at every byte across
> > buckets and brigades is going to slow things down. With 2.0 admins will
> > need to do a more judicious job of bringing filters into play (like not
> > running all .html and .shtml files through mod_include).
> Umh... that's bogus.  There is no reason and no way that simply having a
> file parsed for SSIs should have to be that slow.  I hope there is
> something very not right here (ie. room for big performance improvements)
> causing very poor results, but SSIs have always been quite cheap to parse
> (despite what people like saying; traditionally, any overhead has been
> more in the loss of cachability), and it seems pretty weak to take such a
> massive performance hit.  What mod_include is doing is quite simple, and
> running some simple pattern matching over the output just shouldn't be all
> that expensive when the CPU cycles required should be so cheap.
> Lots of sites base lots of stuff on using a bunch of includes.  I just
> want to point out that saying "well, admins will just have to use less
> includes" is not any sort of answer.

I didn't say "admins will just have to use less includes". I said admins might
have to be more careful about allowing things that don't use includes to be
run through the filter.

And, yes, there are things that leave room for improvement in the filter code.
The biggest piece of overhead is on the bucket allocation code. In my profiling
the malloc and free code was always tops. It made it tough to identify anything
in mod_include itself. So, for the moment, it isn't bogus to say that a filter
- any filter - will provide some processing expense.

Paul J. Reder
"The strength of the Constitution lies entirely in the determination of each
citizen to defend it.  Only if every single citizen feels duty bound to do
his share in this defense are the constitutional rights secure."
-- Albert Einstein

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