Re: [PATCH] x86: Allow NR_CPUS=1024
From: Russ Anderson
Date: Mon Nov 04 2013 - 10:56:32 EST
On Mon, Nov 04, 2013 at 09:16:16AM -0500, Josh Boyer wrote:
> On Mon, Nov 04, 2013 at 03:10:51PM +0100, Ingo Molnar wrote:
> > * Josh Boyer <jwboyer@xxxxxxxxxx> wrote:
> >
> > > > Why touch MAXSMP at all? It's really just a shortcut for 'configure
> > > > the kernel silly large', via a single option, nothing else. You are
> > > > not forced to use it and it should not affect configurability of
> > > > NR_CPUS.
> > > >
> > > > What we _really_ want here is to fix NR_CPUS setting: to extend its
> > > > range and to enforce that NR_CPUS cannot be set larger than 512
> > > > without setting CONFIG_CPUMASK_OFFSTACK.
> > >
> > > OK. I was just thinking that if we've come to the conclusion that 4096
> > > CPUs isn't silly large anymore, we should make MAXSMP be something we
> > > consider silly large. [...]
> >
> > MAXSMP is also supposed to track the real hardware max as well on x86 -
> > i.e. we should only increase it to 8192 etc. if such hardware exists.
>
> Russ, does SGI (or anyone else that you know of) have x86 hardware with
> more than 4096 CPUs?
Yes. We have a system in the lab with 254 12-core IVB sockets for
a total of 3048 cores. With HT is it 6096 cpus.
> If so, I can actually make a bump to the MAXSMP count a separate patch.
>
> josh
--
Russ Anderson, OS RAS/Partitioning Project Lead
SGI - Silicon Graphics Inc rja@xxxxxxx
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