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From Cliff Woolley <>
Subject RE: [PATCH] convert worker MPM to leader/followers design
Date Thu, 11 Apr 2002 23:38:28 GMT
On Thu, 11 Apr 2002, Ryan Bloom wrote:

> > > And you can always play some games with the counters to enable you
> > > to accept a few additional connections (however you define 'few')
> > > in order to keep some work in the queue.
> >
> > It just is hard to think about what "few" should be given that there
> > is always a spastic case (all threads handling large DAV transactions
> > from deep space probes).  But in practice the normal definition of
> > "few" should be fine :)
> I was thinking that the definition of "few" could be a directive.

My take on it is that any non-zero fixed number, configurable or not, is
just as wrong as any other, in the sense that it does not eliminate the
problem, it just just changes how many clients can be affected by it.

That said, I think the idea of shortening the queue would help.  It most
likely doesn't need to be as big as the number of worker threads.
However, it's hard to say what "the right length" is, because that number
changes dynamically.  Ideally, the listener thread would be able to tell
how long its workers spent on requests on average, and adjust the queue
length dynamically in a sort of feedback loop.

That way the listener thread will always have work to do for for the
workers as absolutely soon after the finish the last one as possible
(that's the point of the per-process queue as I understood it), and it
allows listeners who know that their workers are all tied up to avoid
shanghaiing more clients than they expect to be able to deal with in the
near future.

Just a thought.


   Cliff Woolley
   Charlottesville, VA

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