[GE users] io usage always zero on Linux?

Andreas.Haas at Sun.COM Andreas.Haas at Sun.COM
Mon Nov 12 14:54:01 GMT 2007


On Mon, 12 Nov 2007, Michael van Elst wrote:

> On Mon, Nov 12, 2007 at 01:20:09PM +1100, jallen at it.uts.edu.au wrote:
>
>> It looks like mem and cpu get some usage values reported, but never I/O.
>> Does anybody know what the "io" actually reports and if it is supposed to
>> work under Linux?
>
> This is the resource usage as reported by the kernel. For Linux, see
> "man 2 getrusage":
>
>  The  above  struct  was  taken  from  4.3BSD  Reno.  Not all fields
>  are meaningful under Linux.  In linux 2.4 only the fields ru_utime,
>  ru_stime, ru_minflt, and ru_majflt are maintained.  Since Linux
>  2.6, ru_nvcsw and ru_nivcsw are also maintained.
>
> If nothing changed recently then Linux doesn't maintain a per-process
> usage value for I/O operations.
>
> You can get the total number and size of I/O operations for the system
> (using things like sar). If you have only one job slot per machine this
> might be sufficient as a metric.

You mean context number of switches could be suited for measuring I/O 
operations? Wouldn't ru_inblock/ru_oublock be better suited, if these
numbers were multiplied with the size of a block?

Regards,
Andreas

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