linux-kernel - Re: nr_cpu_ids vs AMD 3970x(32 physical CPUs)

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Message-ID: <20200703174539.GA4800@hirez.programming.kicks-ass.net>
Date:   Fri, 3 Jul 2020 19:45:39 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Gabriel C <nix.or.die@...glemail.com>
Cc:     Uladzislau Rezki <urezki@...il.com>,
        LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: nr_cpu_ids vs AMD 3970x(32 physical CPUs)

On Fri, Jul 03, 2020 at 07:07:39PM +0200, Gabriel C wrote:

> I boot all the boxes restricting the cores to the correct count on the
> command line.

This, because you're right about the wasted memory.

> Wasted resource or not, this is still a bug IMO.

Yeah, but not one we can do much about I think. It is the BIOS saying it
wants more because it expects someone to come along and stick another
CPU in.

Possible we could say that for single socket machines overprovisioning
is 'silly', but then, I've no idea how to detect that. You'll need to
find an ACPI person.