Re: maximum number of CPUs

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Thu, Feb 23, 2012 at 08:58:45PM +0000, Mindaugas Rasiukevicius wrote:
> Brook Milligan <brook%nmsu.edu@localhost> wrote:
> > I understand that at least on the i386/amd64 ports CPUs are tracked
> > with a 32-bit mask and thus at most 32 CPUs may be active.  How complex
> > is the task of removing this limitation so that a larger number of CPUs
> > may be used?
> 
> I have a preliminary patch to support up to 255 CPUs on amd64 (not worth
> on i386), however there is still some bug in the early initialisation code,
> when TLBs are not being flushed.  I have not had time yet to debug it out.
> 
> http://www.netbsd.org/~rmind/x86_256_cpus_v4.diff
> 
> Apart from that bug, it should be mostly complete.

It looks like the patch need to be updated for the latest Xen pmap :)

Please make as little assumption as possible about the number of
CPUs Xen supports. I need to do a bit more reverse-ingeenering on
the interface, but I guess hypercalls like MMUEXT_INVLPG_MULTI takes
an array of uint32_t, so we can use more than 32 cpus here as well.

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
--