Re: isolcpus weirdness

Emmanuel Pacaud
2006-02-23T13:07:41Z

Le jeudi 23 février 2006 à 23:21 +1100, Nick Piggin a écrit :
> Emmanuel Pacaud wrote:
> > Hi,
> >
> > When specifying isolcpus kernel parameters, isolated cpu is always the
> > same, not the one I asked for.
..
> >
> > What's wrong ?
> >
>
> If you have 2 CPUs, and "isolate" one of them, the other is isolated
> from it. Ie. there is no difference between isolating one or the other,
> the net result is that they are isolated from each other.
>

>From kernel-parameters.txt:

+ isolcpus= [KNL,SMP] Isolate CPUs from the general scheduler.
+ Format: <cpu number>, ..., <cpu number>
+ This option can be used to specify one or more CPUs
+ to isolate from the general SMP balancing and scheduling
+ algorithms. The only way to move a process onto or off
+ an "isolated" CPU is via the CPU affinity syscalls.
+
+ This option is the preferred way to isolate CPUs. The
+ alternative - manually setting the CPU mask of all tasks
+ in the system can cause problems and suboptimal load
+ balancer performance.

There's a difference between isolated cpus and other cpus: by default,
there's almost no activity on isolated ones. That's what I want to be
able to do.

Emmanuel.