CONFIG_NR_CPUS

[Gilboa Davara]

On Sun, May 20, 2012 at 4:07 AM, Josh Boyer <jwboyer at redhat.com> wrote:
>
> On Sat, May 19, 2012 at 02:54:33PM +0200, Xose Vazquez Perez wrote:
> >
> > >* Tue Jan 17 2012 Dave Jones <davej at redhat.com>
> > >- Rawhide builds now use MAXSMP on x86.
> > >- For release builds, set x86-64 to support 64 CPUs.
> > >  If larger systems become widespread, we can increase in an update.
> >
> > _today_
> >
> > amd:   4sockets * 16cores = 64
>
> Awesome.  Got that covered still.
>
> > intel: 4sockets * 10cores * 2threads = 80
>
> Which particular CPU/Motherboard combo is that, and how often do we see
> it in Fedora?
>
> I'm not opposed to bumping it up to 128 or something, but I'm curious
> how many people are actually going to see benefits.
>
> josh

At least in my case I did run Fedora 12-16 on 4S and 8S machines to
test software scalability on (extreme) high-end hardware.
Though, IMHO anyone that's crazy enough to run Fedora on a high-end
4S/8S machine is more than capable of rebuilding the kernel with
CONFIG_NR_CPUS 256...

However, given the fact that x86_64 machines tend to be far less
memory constrained than i686 machines, I doubt that raising the limit
to 128 will cause too many issues. (Isn't NR_CPUS == 512 in el6?)

- Gilboa