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

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Message-ID: <016d8cff-efc3-4ef1-9aff-7c21c48f2d69@redhat.com>
Date: Tue, 7 May 2024 10:13:32 +0200
From: David Hildenbrand <david@...hat.com>
To: John Hubbard <jhubbard@...dia.com>, Andy Lutomirski <luto@...nel.org>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>,
 Peter Zijlstra <peterz@...radead.org>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
 x86@...nel.org, "H . Peter Anvin" <hpa@...or.com>,
 LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
 Peter Xu <peterx@...hat.com>, Axel Rasmussen <axelrasmussen@...gle.com>
Subject: Re: [PATCH] x86/fault: speed up uffd-unit-test by 10x: rate-limit
 "MCE: Killing" logs

The patch subject is misleading. This should be "don't flood the system 
log". Nobody cares about the speed of a unittest ;)

On 07.05.24 04:29, John Hubbard wrote:
> If a system experiences a lot of memory failures, then any associated
> printk() output really needs to be rate-limited. I noticed this while
> running selftests/mm/uffd-unit-tests, which logs 12,305 lines of output,
> adding (on my system) an extra 97 seconds of runtime due to printk time.

Recently discussed:

https://lkml.kernel.org/r/a9e3120d-8b79-4435-b113-ceb20aa45ee2@alu.unizg.hr

See the pros/cons of using ratelimiting, and what an alternative for 
uffd is that Axel is working on.

(CCing Peter and Axel)

-- 
Cheers,

David / dhildenb