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From Jeff Trawick <>
Subject Re: Comments on accept-mutex/single-listen patch ??
Date Tue, 28 Aug 2001 15:35:36 GMT
Ryan Bloom <> writes:

> > > >why is SingleListen needed?
> > >
> > > Pretty much to make SINGLE_LISTEN runtime rather than compile
> > > time... Again, to give the admins more control over how
> > > Apache handles mutexing.
> >
> > I'm not totally against it, it just seems that it is for playing
> > around (sort of like USE_NONE_SERIALIZED_ACCEPT) or trying to work
> > around an Apache bug (i.e., maybe there is some platform/version where
> > we're supposed to turn on SINGLE_LISTEN_UNSERIALIZE_ACCEPT but don't).
> > Why can't they compile this in?  This would seem to be useful in
> > extremely rare circumstances, and only for somebody who really knows
> > what they are doing.
> I disagree.  Compiling in SINGLE_LISTEN_UNSERIALIZE_ACCEPT means that
> I have to no up front exactly how the server will be used.  What if I am compiling
> one binary to be used on 50 machines (big fortune 2500 companies do this a lot,
> so that they have a common interface).  On some of those machines (intranet),
> I may only want one port, so I want to be able to use S_L_U_A, on others
> (Internet), I want two ports (one SSL on regular), so I don't want to use S_L_U_A.

S_L_U_A already handles this capability.  When S_L_U_A is defined, you
still get a mutex when there is more than one port.  You skip the
mutex only when there is a single port (hence the leading "S_L_").

> I have always thought that being able to turn this on and off at run-time would
> be very cool and useful.

The directive would seem to only be useful for a platform/version that
has no thundering herd problem with accept() and where Apache's
ap_config.h has not yet been tweaked to indicate that.  Is this a
real-life problem that we need to solve, or is it rare enough that the
user can use the existing compile-time mechanism until Apache's
ap_config.h is fixed and we can avoid adding another directive.

Jeff Trawick | | PGP public key at web site:
             Born in Roswell... married an alien...

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