Re: hrProcessorLoad returns incorrect values for processor #'s > 100

On 17 July 2012 19:34, Joe Guderjohn <[email protected]> wrote:
> Platform: IBM 3850 (10.1.20.10) w/ 16 CPUs, each with 8 cores = 128 CPUs for
> monitoring
> Net-snmp version: 5.3.2.2 (RHEL 5.6). Also built net-snmp-5.4.4 with same
> results.
>
> Values returned for hrProcessorLoad for CPU #’s greater than 100 appear to
> be incorrect. They’re always in the range of 90 > 100.

> I’d be happy to try and solve this, if someone would suggest a few source
> files that might have some bearing on this.


Hmmm...   that sounds an interesting one.

The souce code that implements the hrProcessorTable is in
   agent/mibgroup/host/hr_proc.c
but that relies on data from the "hardware independence layer"
which is implemented at
   agent/mibgroup/hardware/cpu/*

I suspect the file that is probably most relevant here will be
   agent/mibgroup/hardware/cpu/cpu_linux.c
(though you can check by seeing which files in the directory
actually get compiled!).

I've had a quick look, and can't immediately spot an limitations of <100

The data is being read from
    /proc/cpuinfo   &    /proc/stat
(plus /proc/vmstat, but that's probably not relevant here)

It might be worth checking those two files, to see if you
can spot anything odd about the higher entries.

<ping>
I think this may be related to line 156 of cpu_linux.c

           b1 = b2+5; /* Skip "cpuN " */

This works fine with single-digit CPU numbers,
and happens to work with double-digit CPU numbers
(but leaves the trailing space for the next sscanf to ignore)
But with three CPU numbers, the third digit will be left
in the buffer, and picked up by the next sscanf statement (line 160)

Try tweaking this b1 line to skip the next token,
rather than moving on a fixed amount.
   I strongly suspect that should do the trick

Dave

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