linux-kernel - Re: [PATCH] x86/fault: speed up uffd-unit-test by 10x: rate-limit "MCE: Killing" logs

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Message-ID: <20240507192650.GJZjqAeipgUw2AoCK9@fat_crate.local>
Date: Tue, 7 May 2024 21:26:50 +0200
From: Borislav Petkov <bp@...en8.de>
To: John Hubbard <jhubbard@...dia.com>
Cc: Andy Lutomirski <luto@...nel.org>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	"H . Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: [PATCH] x86/fault: speed up uffd-unit-test by 10x: rate-limit
 "MCE: Killing" logs

On Mon, May 06, 2024 at 07:29:39PM -0700, John Hubbard wrote:
> Generating lots of memory poisoning events seems like a valid use case,
> by which I mean that this is not just a testing artifact. And that's why
> the fix applies to the code that directly generates the output, rather
> than the selftest that triggers it.

Sorry, not taking a "fix" for something hypothetical.

If this is a real issue on a real system and the printing is the
*actual* problem at hand in a hw error storm sure, but no, not because
a selftest runs slower.

I'm pretty sure in a hw error storm scenario, printk being slow is the
least of your problems.

And in such a scenario the *last* thing you wanna do is ratelimit prints
so that you can't even get all the logs which is *the* thing you need to
debug the hw.

Thx.

-- 
Regards/Gruss,
    Boris.

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