whats going on with the scheduler?

Andy Farkas andyf at speednet.com.au
Tue Jul 8 15:40:44 PDT 2003


On Tue, 8 Jul 2003, Doug White wrote:

> On Tue, 8 Jul 2003, Andy Farkas wrote:
>
> > Any other ideas? Why would 3 (niced) cpu intensive processes suddenly get
> > reduced cpu time (on a 4 cpu system) when a 4th non-resource intensive
> > process gets started?
>
> Hm.. guess its time to explain how nice works again.
>
> Nice is a relative value.  If you have 2 processes in a system, one with a
> lower nice value (== higher "priority") than the other, the lower-niced
> process will be scheduled in deference to the higher-niced process.  The
> scheduler attempts to ensure that niced processes are not starved.  (In
> practice, nice level 20 gets some special treatment.)

That doesn't explain why the idle time goes up, in my case.

If you have 4 processors in a box and start 3 cpu-intensive jobs, the
system load will be 3.00 and idle time will be 25%. If you start another
semi cpu-intensive process, one would expect the load to increase and the
idle time to come down, regardless if the other 3 procs are niced or not.

ps. setiathome procs run at idle level 15.

--

 :{ andyf at speednet.com.au

        Andy Farkas
    System Administrator
   Speednet Communications
 http://www.speednet.com.au/






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