linux-kernel - Re: [PATCH v5 2/7] x86/mm: Use a single cache hot per-CPU variable to record pgdir

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Message-ID: <20250520143532.GMaCyTNJqH_T2LR8q5@fat_crate.local>
Date: Tue, 20 May 2025 16:35:32 +0200
From: Borislav Petkov <bp@...en8.de>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: "Kirill A. Shutemov" <kirill@...temov.name>,
	Ard Biesheuvel <ardb+git@...gle.com>, linux-kernel@...r.kernel.org,
	x86@...nel.org, Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Brian Gerst <brgerst@...il.com>
Subject: Re: [PATCH v5 2/7] x86/mm: Use a single cache hot per-CPU variable
 to record pgdir_shift

On Tue, May 20, 2025 at 01:28:52PM +0200, Ard Biesheuvel wrote:
> Are you saying we shouldn't optimize prematurely? You must be new here :-)

Right, but do you see __pgdir_shift on a seriously hot path to warrant this?

I'd expect this to happen the other way around, really: "Hey, pgdir_shift is
getting accessed a lot, let's stick it somewhere where we can access it
quickly..."

Thx.

-- 
Regards/Gruss,
    Boris.

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