Re: [PATCH] x86/smpboot: Make logical package management more robust

Peter Zijlstra
2016-12-08T13:04:47Z

On Thu, Dec 08, 2016 at 01:49:28PM +0100, Thomas Gleixner wrote:
>
> > > - if (logical_packages > __max_logical_packages) {
> > > - pr_warn("Detected more packages (%u), then computed by BIOS data (%u).\n",
> > > - logical_packages, __max_logical_packages);
> > > - logical_packages_frozen = true;
> > > - __max_logical_packages = logical_packages;
> >
> > So we'll never 'shrink' the initially computed max; which could result
> > in using more memory than strictly needed, otoh it makes physical
> > hotplug happier.
>
> Yes. I was debating that back and forth and at the end decided that making
> it simple and robust is a good tradeoff vs. the slightly higher memory
> consumption. Though on most systems that's a non issue as number of
> possible cpus/packages is the same as the actual available ones. The insane
> setups have to suffer - rightfully so.

Don't we overestimate by a factor of 2 due to HT? That is, every single
socket Intel box will have a max_packages of 2.

Not that I care too deeply, and arguably the HT case _is_ insane because
its impossible to tell etc..