On Tue, Jul 18, 2000 at 12:48:41AM -0000, Stuart Cooper wrote:
> Original problem: Can I specify which processes run on which CPUs in
> Linux?
>
> You should get the performance you need from out of the box scheduling. While
Depends what performance you need.
Linux has a fairly generic scheduler, with is not configurable (beyond
nice). Consider if you had the following :
A machine with 4 CPUs, running 16 different processes, all of which will
use as much CPU as you throw at them. Using the standard scheduler, each
process will get about 1/4 of a CPU, which is generally what you want.
However, say you wanted one of these processes to use 1 entire CPU, and
the other 15 to fight over the remainign 3 CPUs (ie, 1/5 of a CPU each).
This can not be done with the default scheduler.
(Yes, it may be possible with nice, but consider 2 processes sharing 1 CPU,
14 getting the other 2 - cant be done with nice).
I'm not aware of any patches to give processor sets under Linux, however
there's at least two patches which implement fair-share scheduling
(although I think only one of them works under SMP) which could probably
be setup to give a similar result.
Fair-share scheduling basically gives a percentage of the total CPU time
to groups of processes, so in the example above you'd give 25% of your
CPU time to the 1 processes, and the remaining 75% to the other 15
processes.
Scott.
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