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From "Rose, John B" <jbr...@utk.edu>
Subject Re: [users@httpd] What is the impact of setting ServerLimit higher than MaxClients?
Date Tue, 20 Aug 2013 21:30:56 GMT
Can you expand on this a bit?

"But you could measure actual shm use with diff values."

Thanks

From: Jeff Trawick <trawick@gmail.com<mailto:trawick@gmail.com>>
Reply-To: "users@httpd.apache.org<mailto:users@httpd.apache.org>" <users@httpd.apache.org<mailto:users@httpd.apache.org>>
Date: Tuesday, August 20, 2013 5:13 PM
To: "users@httpd.apache.org<mailto:users@httpd.apache.org>" <users@httpd.apache.org<mailto:users@httpd.apache.org>>
Subject: Re: [users@httpd] What is the impact of setting ServerLimit higher than MaxClients?


On Aug 20, 2013 5:05 PM, "Rose, John B" <jbrose@utk.edu<mailto:jbrose@utk.edu>>
wrote:
>
> Thanks for replying.
>
> Yes, it is prefork MPM.
>
> Reading this in the Apache documentation …
>
> "Do not set the value of this directive any higher than what you might want to set MaxClients
to."
>
> It also says …
>
> "Special care must be taken when using this directive. If ServerLimit is set to a value
much higher than necessary, extra, unused shared memory will be allocated"
>
> What is classified as "much higher?"
>
> Is there a negative (or positive) impact of any kind of, for example, setting ServerLimit
to 2000 and MaxClients to 512?

Unclear what much higher means, especially on a modern machine.  I'd be extremely surprised
if 2000 has any noticeable impact.  But you could measure actual shm use with diff values.
>
> http://httpd.apache.org/docs/2.2/mod/mpm_common.html#serverlimit
>
> Thanks
>
>
> From: Jeff Trawick <trawick@gmail.com<mailto:trawick@gmail.com>>
> Reply-To: "users@httpd.apache.org<mailto:users@httpd.apache.org>" <users@httpd.apache.org<mailto:users@httpd.apache.org>>
> Date: Tuesday, August 20, 2013 4:50 PM
> To: "users@httpd.apache.org<mailto:users@httpd.apache.org>" <users@httpd.apache.org<mailto:users@httpd.apache.org>>
> Subject: Re: [users@httpd] What is the impact of setting ServerLimit higher than MaxClients?
>
> On Aug 20, 2013 4:26 PM, "Rose, John B" <jbrose@utk.edu<mailto:jbrose@utk.edu>>
wrote:
> >
> > What is the impact of setting the ServerLimit to a value significantly more than
your MaxClients value? Say with a MaxClients set to 512 and ServerLimit of 2000?
> >
>
> Assuming prefork MPM:
>
> You can increase maxclients across graceful restart, up to serverlimit
>
> Threaded MPMs: comparing maxclients vs server limit doesn't work without also accounting
for threadsperchild
>
> >
> >

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