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From Brian Pane <>
Subject Re: worker mpm -- fdqueue question
Date Wed, 07 Aug 2002 16:52:12 GMT
Aaron Bannert wrote:

>On Wed, Aug 07, 2002 at 09:09:41AM -0700, Ian Holsman wrote:
>>wouldn't this lead to starvation on a busy system?
>What kind of starvation?

For a stack-based implementation in general (though not
our fdqueue in particular), the failure case looks like this:

If the rate of incoming connections increases until it matches
or exceeds the rate at which busy workers finish handling
their current connections, the listener will keep putting
new connections on the top of the stack at least as fast
as the workers can consume them.  When this happens, older
connections at the bottom of the stack never get processed
until the rate of incoming connections drops.

Fortunately, though, our logic to throttle the listener
based on the number of idle workers ensures that the
number of connections in the queue can't exceed the number
of idle workers.  So there should always be an idle worker
available to pick up any connection currently in the fdqueue.


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