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From: Thomas Gleixner <tglx@linutronix.de>
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To: Linus Torvalds <torvalds@linuxfoundation.org>
Cc: Guenter Roeck <linux@roeck-us.net>, LKML <linux-kernel@vger.kernel.org>,
 x86@kernel.org, Uros Bizjak <ubizjak@gmail.com>,
 linux-sparse@vger.kernel.org, lkp@intel.com,
 oe-kbuild-all@lists.linux.dev, Arnd Bergmann <arnd@kernel.org>
Subject: Re: [patch 5/9] x86: Cure per CPU madness on UP
In-Reply-To: <877ci3j80k.ffs@tglx>
References: <20240303235029.555787150@linutronix.de>
 <20240304005104.622511517@linutronix.de>
 <e20d88d0-5fb9-4307-be67-88b04ae9a188@roeck-us.net>
 <CAHk-=whK=G1o6RtS9DS3wEGF1KU7WLgLL1+6Se86bj8m7wwqrQ@mail.gmail.com>
 <87y1ajjsv9.ffs@tglx> <87o7bfjeae.ffs@tglx>
 <CAHk-=wiP+XMGHr8NU13sSOG_oasNZN02O9_c1PzCJNG7+O-GPw@mail.gmail.com>
 <877ci3j80k.ffs@tglx>
Date: Mon, 18 Mar 2024 18:27:55 +0100
Message-ID: <87le6fih5w.ffs@tglx>
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On Sat, Mar 16 2024 at 02:11, Thomas Gleixner wrote:
> On Fri, Mar 15 2024 at 16:23, Linus Torvalds wrote:
> The amount of subtle SMP=n fallout has been kinda exponentially
> increasing over the years and it's just putting burden on the wrong
> people. TBH, I'm tired of this nonsense.

And for the fun of it I hacked Kconfig to allow a SMP=y NR_CPUS=1 build
and checked the size of vmlinux:

                64-bit          32-bit
SMP, NCPUS=1    38438400        22110177
UP              38393703        21682041
Delta              44697          428076
                     0.1%              2%              

The UP savings are not really impressive...

Let me look what it actually takes to do that.

Thanks,

        tglx