[PATCH 0/1] [Yakkety] UBUNTU: [Config] Increase the NR_CPUS to 8K for amd64 to support systems with a large number of cores.

[Seth Forshee]

On Tue, Nov 22, 2016 at 08:35:17AM -0800, Brad Figg wrote:
> On Tue, Nov 22, 2016 at 03:49:25PM +0000, Colin Ian King wrote:
> > On 22/11/16 15:35, Brad Figg wrote:
> > > BugLink: http://bugs.launchpad.net/bugs/1579205
> > > 
> > > Brad Figg (1):
> > >   UBUNTU: [Config] Increase the NR_CPUS to 8K for amd64 to support
> > >     systems with a     large number of cores.
> > > 
> > >  debian.master/config/amd64/config.common.amd64 | 2 +-
> > >  debian.master/config/annotations               | 2 +-
> > >  2 files changed, 2 insertions(+), 2 deletions(-)
> > > 
> > 
> > What's the overhead or impact of bumping this to 8K?
> > 
> > Colin
> 
> I'm not sure. However, Tim looked at this once before and found it wasn't
> significant if I remember right. This patch is a resubmit of one that was
> submitted, applied and the dropped mistakenly.

According to the Kconfig documentation for NR_CPUS, "each supported CPU
adds approximately eight kilobytes to the kernel image." If we assume
that is correct we're talking ~64MB of extra RAM. I'd be surprised if
anyone is actually keeping that estimate up to date though.

Tim - I don't suppose you still have the number you came up with before?
It would be nice to have an idea - cloud people may be upset if it turns
out to be a lot.