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From: Stefan Fritsch <sf@sfritsch.de>
To: dev@httpd.apache.org
Subject: Re: svn commit: r1202255 -
 /httpd/httpd/trunk/modules/filters/mod_reqtimeout.c
Date: Tue, 15 Nov 2011 19:33:12 +0100
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On Tuesday 15 November 2011, Paul Querna wrote:
> On Tue, Nov 15, 2011 at 9:17 AM, Stefan Fritsch <sf@sfritsch.de> 
wrote:
> > On Tue, 15 Nov 2011, pquerna@apache.org wrote:
> >> Author: pquerna
> >> Date: Tue Nov 15 15:49:19 2011
> >> New Revision: 1202255
> >> 
> >> URL: http://svn.apache.org/viewvc?rev=1202255&view=rev
> >> Log:
> >> disable mod_reqtimeout if not configured
> > 
> > Why that? We have just changed the default to be enabled in
> > r1199447 and several developers at the hackathon agreed to this
> > change.
> 
> Didn't know it was discussed in depth at the hackathon, and there
> wasn't any discussion on the list....
>
> It showed up quite quickly in my profiling of the Event MPM,
> because every pull/push on the filters would cause a
> apr_time_now() call.
> 
> I don't really like that just by loading the module, it changes the
> behavior and performance of the server so drastically.

It only acts on reads from the client. Normal non-POST requests arrive 
in one or two packets, which would mean approx. 3 additional 
apr_time_now calls per request. I haven't done benchmarks, but I can't 
imagine that this has a drastic impact on performance. And if it costs 
1-2%, then that's a small cost compared to the impact of slowloris 
type attacks which eat lots of memory.

The general intention of the recent changes in default configs and 
module selection/loading was to make it easier to only load those 
modules that are really needed, have a reasonable default config, and 
have the compiled-in default values be the same as those in the 
example config files.