linux-kernel - Re: [GIT PULL] bitmap changes for v6.0-rc1

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Date:   Mon, 10 Oct 2022 14:18:46 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Yury Norov <yury.norov@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>
Subject: Re: [GIT PULL] bitmap changes for v6.0-rc1

On Mon, Oct 10, 2022 at 2:12 PM Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
>
> On Sun, Oct 2, 2022 at 7:03 PM Yury Norov <yury.norov@...il.com> wrote:
> >
> >       lib/cpumask: add FORCE_NR_CPUS config option
>
> Side note: I think we should make this option depend on EXPERT.

Oh, and if a constant 'nr_cpu_ids' is such an important thing from a
code generation standpoint, maybe we'd be better off saying 'for small
NR_CPUS, just make nr_cpu_ids be that small constant".

Rather than confusing people with a question that is a bit strange.
Afaik, all our kernel code has to work with "nr_cpu_id's doesn't match
the number of CPU's we actually have", because of cpu hotplug (and
suspend/resume) issues anyway.

So I _think_ all the nr_cpu_id's games are mainly because we don't
want to allocate huge arrays when  you can't actually have that many
CPU's - but for a small NR_CPUS situation that just isn't an issue
anyway.

Yes? No?

              Linus