Command Buffer

[Ruiz, Francisco]

Ah. Thanks for the update. 

So just to reiterate, it sounds like the command buffer goes hand in
hand with default pipe size. So if the kernel value is only set to 4k,
then the max size of the command buffer will also be 4k. Is this
correct?

Is there any recommendations on what to set the kernel value to for
32-bit, 2.6 kernels?

Thanks!
Frank


-----Original Message-----
From: Andreas Ericsson [mailto:ae at op5.se] 
Sent: Monday, August 15, 2005 4:03 PM
To: Ruiz, Francisco
Cc: Nagios User List
Subject: Re: [Nagios-users] Command Buffer

Ruiz, Francisco wrote:
> Greetings,
> 
> I was hoping someone could elaborate more on the command buffer, and
> what the significance is of going from 4k to 32k.
> 

The size of IPC pipes (FIFO's) is specified in the kernel of your OS. 
You can set it to whatever you like, but you might run into weird things

depending on your system type. For instance, on most 32-bit 
architectures the kernel allocates memory in blocks of 4096 bytes, so 
that's the size of a FIFO. If you make the FIFO bigger, the kernel needs

to do exception handling when you write anything larger than that to the

pipe, and if it doesn't you'll end up with either a message that get's 
truncated anyway or something undefined.

What you WILL get is performance that's about 1/3 of what you'd get if 
you don't meddle with it.

For reference, Linux users have reported this to work splendidly on 
kernels since 2.4.20, although the code suggests that FIFO handling 
changed quite a bit somewhere in 2.3 and there-about.

> Thanks! 
> 
> 
> 
> 
> -------------------------------------------------------
> SF.Net email is Sponsored by the Better Software Conference & EXPO
> September 19-22, 2005 * San Francisco, CA * Development Lifecycle
Practices
> Agile & Plan-Driven Development * Managing Projects & Teams * Testing
& QA
> Security * Process Improvement & Measurement *
http://www.sqe.com/bsce5sf
> _______________________________________________
> Nagios-users mailing list
> Nagios-users at lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/nagios-users
> ::: Please include Nagios version, plugin version (-v) and OS when
reporting any issue. 
> ::: Messages without supporting info will risk being sent to /dev/null
> 

-- 
Andreas Ericsson                   andreas.ericsson at op5.se
OP5 AB                             www.op5.se
Lead Developer


-------------------------------------------------------
SF.Net email is Sponsored by the Better Software Conference & EXPO
September 19-22, 2005 * San Francisco, CA * Development Lifecycle Practices
Agile & Plan-Driven Development * Managing Projects & Teams * Testing & QA
Security * Process Improvement & Measurement * http://www.sqe.com/bsce5sf
_______________________________________________
Nagios-users mailing list
Nagios-users at lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/nagios-users
::: Please include Nagios version, plugin version (-v) and OS when reporting any issue. 
::: Messages without supporting info will risk being sent to /dev/null