linux-kernel - RE: [PATCH v2 1/5] smp: don't declare nr_cpu_ids if NR

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Date:   Wed, 7 Sep 2022 08:02:42 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Peter Zijlstra' <peterz@...radead.org>,
        Yury Norov <yury.norov@...il.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Andy Shevchenko" <andriy.shevchenko@...ux.intel.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        "Vlastimil Babka" <vbabka@...e.cz>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        "Valentin Schneider" <vschneid@...hat.com>,
        Sander Vanheule <sander@...nheule.net>,
        Alexey Klimov <klimov.linux@...il.com>,
        Eric Biggers <ebiggers@...gle.com>
Subject: RE: [PATCH v2 1/5] smp: don't declare nr_cpu_ids if NR_CPUS == 1

From: Peter Zijlstra
> Sent: 06 September 2022 15:37
...
> It was suggested the other day we remove a whole bunch of SMP=n code and
> unconditionally use SMP code, even if its pointless on UP just to make
> the source simpler.

All the world isn't x86.

There are some small embedded systems which are definitely UP
and where you don't want any of the SMP 'bloat'.
Architectures like NiosII will only ever be SMP.

There certainly have recently been (and probably still are)
small ppc cpu for embedded systems that are UP.

	David

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