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From Nick Kew <>
Subject Re: keepalivetimeout and 2.2 configs
Date Mon, 11 Apr 2005 10:41:08 GMT
Joshua Slive wrote:
> On Sun, 10 Apr 2005, Rich Bowen wrote:
>> On the more practical non-gut-feeling side, I've found consistently that
>> changing KeepAliveTimeout from 15 to 3 immediately, and drastically,
>> reduces server load on busy servers, where a significant percentage of
>> the child processes are in Keepalive mode most of the time.

Yes, that seems to be rather common in busy servers, and applies to
worker as well as prefork.

> - It's always a trade-off between the memory used by the idle worker and
> the performance cost of setting up and tearing down connections.
> Different sites care about those resources to different degrees.

Indeed.  But something like 4 seconds seems to work well in real life.
It is essentially about fetching included contents on a persistent

> - This is highly mpm-dependent.  For threaded mpms, the cost of an idle
> worker is lower.

But nevertheless critical on some busy servers.

>	  For the new event mpm, the problem goes away entirely,
> and you are better off with a much *higher* timeout.  So pushing event
> up the list of recommended mpms would be the best way to solve this.

Indeed.  This needs to be documented more completely, too.  I've got
something here I can probably contribute if I can find the right place
to insert it in the existing docs.

>	  It
> would be nice if other mpms were a little more flexible about KeepAlive
> policy, like by lowering the timeout when you get near MaxClients.

Indeed.  Configurable Min/Max for Keepalive?

> - This should be solved in the code-default, not the config-file
> default. The directive will not exist in the default config file in

Aaargh!  That *will* upset admins who *know* from experience that
they *need* to reduce it.

> - 2-3 seconds seems too short for modem or high-latency connections. 
> 5-10 seems more in the ballpark.

AFAIK the highest-latency connections in significant numbers in the
wild come from mobile phones, and can be around 4 secs for new (not
keepalive) connections.

But it's definitely something that a server admin wants some
control over.

Nick Kew

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