RE: snmpd high CPU usage - polling rate?

Dave,

Thanks for the response.  I discovered the new caching behavior when I moved to 5.4.  We ended up patching the code to refresh the counters in IF-MIB every 125ms (twice our polling rate), using the "enable-mini-agent" option, and loading in only the IF-MIB module.  Using this combination, the CPU usage of snmpd is about 3.0% at idle and 4.0% when being queried at 4Hz.  This usage is acceptable for my application.  If anyone is interested in the patch please contact me via email and I'll send you the details.

Thanks again,

-Daniel

-----Original Message-----
From:	[email protected] on behalf of Dave Shield
Sent:	Thu 5/3/2007 5:27 PM
To:	Hackney [US], Daniel H.
Cc:	[email protected]
Subject:	Re: snmpd high CPU usage - polling rate?
[Sorry for the delay in responding]

On 26/03/07, Hackney [US], Daniel H. <[email protected]> wrote:
> I'm running Net-SNMP snmpd version 5.1.2 on Linux 2.6.11.  I have a client
> application that queries the localhost for eight values from IF-MIB using a
> single GetRequest packet.  The query rate is 4Hz.

>  Before I try using the latest version..... I'd
> appreciate an opinion or two from the experts on whether or not polling at
> this rate is reasonable for snmpd in the first place.  Yes, I really need
> the data this often.

Upgrading to newer versions probably isn't going to help you.
The latest code will typically cache the interface statistics for
several seconds, rather than re-reading them afresh every time.
Such versions will probably handle a rapid rate of queries better
than earlier ones, but you'll get the same answers each time
(which rather negates the point!)

There's always a balance between timeliness of the information and
the cost of retrieving this information.  For most modules other than
the most straightforward, I doubt whether a sub-second query rate is realistic.

Dave




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