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From "Ryan Bloom" <...@covalent.net>
Subject RE: worker MPM bugs (was Re: [PATCH] Possible fix for worker MPM performance problem)
Date Thu, 25 Apr 2002 16:57:04 GMT
> From: Aaron Bannert [mailto:aaron@clove.org]


> On Thu, Apr 25, 2002 at 11:30:54AM -0400, Bill Stoddard wrote:
> > Would someone care to see if this fixes the worker MPM performance
> problem reported
> > earlier on the list (request-per-second dropping when clients
exceeded
> threadsperchild)?
> > This patch defers starting the listener untill -all- the workers
have
> started.
> 
> I'm not really sure how this would fix the performance problems, and
given
> the current theory it might even exacerbate it. The current hypothesis
> is that when we run out of available workers in all available
children,
> and we are waiting for a new child to be spawned, connections continue
> to be accepted and placed in a queue*, and as such aren't able to be
> immediately serviced as soon as the new child is started.
> 
> A simple fix would be to prevent the queue* from accepting more
> connections until there is an idle worker thread available. The reason
> I have hesitated to make this change is because it would alter the
> places where the listener thread may enter blocking calls, and would
> probably break graceful/non-graceful restarts. If I get a little
> time I will try to look in to this again this weekend.
> 
> * When I say "queue" I really mean stack. In thinking about this
problem
> over the last few days I realized that we should convert back to a
true
> LIFO, otherwise it is possible for a request to sit at the back of the
> stack for a long time before it is serviced.

I hope you mean FIFO here.  If you use a LIFO, then the first request
received will be the last request served, which is a bad thing.

Ryan



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