unbalanced load

Michal Szymanski <[email protected]> Wed, 18 May 2005 22:48:13 +0200
Newsgroups org.kernel.vger.linux-smp
Message-ID <[email protected]>
Hi,

On 2.6 SMP kernels (running on multi-cpu machines) one can see the
effect called "Light but Unbalanced Load" by Rick Lindsley in his
article "What's New in the 2.6 Scheduler?" 
(http://www.linuxjournal.com/article/7178)

If, say, 3 processes run on a dual-cpu machine, one of them tends to be
bound to one processor, taking 99.9% of cpu time, while two other run
on the second processor, dividing its time more or less 50%-50%
I think this might be considered reasonable (although if the tasks
are not of the same user, it might be unfair) if all the tasks have the
same 'nice level'.

But, I have noticed that even if one of the tasks is niced and two other
- not, it happens that it is the niced process that occupies one cpu
alone, getting 99.9% of the processor time. This seems to be explicitly
contrary to what nice-ing the jobs should do.

Is this 'affinity' or 'cpu-binding' issue controllable somehow (by
setting some kernel parameters, for example)?

thanks in advance for hints,

regards, Michal.

-- 
  Michal Szymanski (msz at astrouw dot edu dot pl)
  Warsaw University Observatory, Warszawa, POLAND