linux-kernel - Re: [PATCH] x86/asm: Use asm_inline() instead of asm() in amd_clear

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Message-ID: <20250316105316.GAZ9atnKtYqZjvS4JY@fat_crate.local>
Date: Sun, 16 Mar 2025 11:53:16 +0100
From: Borislav Petkov <bp@...en8.de>
To: Ingo Molnar <mingo@...nel.org>
Cc: Uros Bizjak <ubizjak@...il.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [PATCH] x86/asm: Use asm_inline() instead of asm() in
 amd_clear_divider()

On Sun, Mar 16, 2025 at 01:37:23AM +0100, Ingo Molnar wrote:
> Yeah, so that's a suboptimal test for these particular changes really: 
> why would a simple CPU-saturated kernel build with low levels of kernel 
> use of the affected areas show measurable changes with this commit?

Thus "Or maybe I need a different benchmark." :)

OTOH, it still tells me that if there are no negative changes in *that*
benchmark, then I should not worry.

> So on my system there appears to be a measurable improvement in 
> performance on this particular benchmark on the order of magnitude of 
> around ~0.8%, which is outside the measurement noise of around ~0.2%.

That's fine. It won't make me fall off my horse but sure, there are some small
improvements. Just don't let code readability suffer along the way with those
exercises.

:-)

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette