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From Doug Bell <d...@plainblack.com>
Subject Re: [users@httpd] How does Prefork work?
Date Thu, 28 May 2009 21:27:29 GMT
On May 28, 2009, at 4:19 PM, CrystalCracker wrote:

>
>>> MaxClients at 250 means that potentially 250 httpd processes can be
>>> running at once. Do you have the memory to support that many without
>>> swapping? Swapping usually ends up killing a system, especially if
>>> it's already handling a lot of disk i/o.
>
> Regarding MaxClients at 250, the only thing that I need to worry  
> about is
> whether I have enough memory for 250 processes if there really are.  
> Right?

Right.

>>> MaxSpareServers at 20 means that at most 20 servers will sit there
>>> idle. MinSpareServers means at least 5 will sit idle.
> So, regardless of how many threads are active (until it reaches
> MaxClients/ServerLimit), apache will always have between  
> MinSpareServers and
> MaxSpareServers ready to serve. Right?

Right. But don't confuse "threads" with "processes". We're talking  
"processes" here.

>>> Does your traffic tend to be steady throughout the day or
>>> does it spike sharply once or more?
>
> I do see some spikes when the system is doing full GC, which  
> sometimes takes
> longer than usual. Thats is like once every week or more. That  
> causes the
> app to slow down, and threads trying to do their jobs pile up over  
> time. And
> then it recovers in a few minutes. At other times, I don't see huge  
> spikes.
> I probably should consider reducing MaxSpareServers to 10.

Also right.


Doug Bell -- Senior Developer, Plain Black Corp.
[ http://plainblack.com ]

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