Re: SMP: bind process to cpu

[Manfred Spraul]

Christoph Hellwig wrote:
> 
> In article <[e-mail]> you wrote:
> > Hi,
> >
> > I run an 3*XEON 550MHz Primergy with 2GB of RAM.
> > On this machine, i have compiled kernel 2.4.0SMP.
> >
> > Is it possible to bind a process to a specific
> > cpu on this SMP machine (process affinity) ?
> 
> Linux 2.4 is mostlu ready for process affinity, but it is not (yet)
> exported to userspace.  I've attached at patch by Nick Pollitt from SGI
> that allows to enable process pinning using prctl().
> 
> > I there something like pset ?
> 
> I've seen patches for SGI-like psets for 2.2.<something>, but not for 2.4.
>
>         Christoph
>
You must also update wake_process_synchroneous(), otherwise you can get
lost wakeups with pipes.

Something like

>         if (!(p->cpus_allowed & (1 << smp_processor_id()))
>                 reschedule_idle(p);

must be added after add_to_runqueue().

Ingo Molnar did some testing with tux2, and under high load wakeups were
lost without such a patch.

--
	Manfred