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From "Akins, Brian" <>
Subject Re: MPMs, COW vs Child Process Spawning
Date Wed, 29 Oct 2008 20:53:48 GMT
One of the things I've noticed on a practical level, is that forked children
in worker wind up being "linearized" within themselves to some extent.
Think of how the buffered logs work in mod_log_config (one buffer protected
by a mutex).  (I can't think of the correct term for it right now. Basically
every thread is waiting on the same mutex eventually.)  This is seen in
other modules...

The fork gets around this somewhat, as there are multiple mutexes
independently locked/unlocked.

If we have one multi-threaded process, this will force us to think about the
performance ramifications of these uses of single mutexes.  For
mod_log_config, for example, a queue with a single writer thread may be the

Brian Akins
Chief Operations Engineer
Turner Digital Media Technologies

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