linux-kernel - Re: [PATCH] x86/mce: Increase the size of the MCE pool from 2 to 8 pages

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Message-ID: <20231016144058.GEZS1LemcrhZvVrC15@fat_crate.local>
Date:   Mon, 16 Oct 2023 16:40:58 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Dave Hansen <dave.hansen@...el.com>
Cc:     Yazen Ghannam <yazen.ghannam@....com>,
        "Sironi, Filippo" <sironi@...zon.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "tony.luck@...el.com" <tony.luck@...el.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>
Subject: Re: [PATCH] x86/mce: Increase the size of the MCE pool from 2 to 8
 pages

On Mon, Oct 16, 2023 at 07:24:34AM -0700, Dave Hansen wrote:
> On 10/16/23 07:14, Yazen Ghannam wrote:
> > 1) Keep the current config size for boot time. 
> > 2) Add a kernel parameter
> > and/or sysfs file to allow users to request additional genpool capacity.
> > 3) Use gen_pool_add(), or whichever, to add the capacity based on user
> > input. Maybe this can be expanded later to be automatic. But I think it
> > simpler to start with explicit user input.
> 
> I guarantee virtually nobody will ever use an explicit kernel interface
> to bump the size up.  It'll be the same exact folks that recompile their
> kernels.
> 
> An automatic resizing one doesn't have to be fancy and only has to
> expand once:

Can we slow down here pls?

You expand once and then that stuck bit error increases its rate of MCEs
reported and all of a sudden that raised size is overflowed again.

Or, you add logic which thresholds duplicate errors similar to the cmci
storm logic we have.

*If* that is the case at all.

So can we analyze first what type of errors are reported and why they're
overflowing the pool before we do ad-hoc hackery?

Thx.

-- 
Regards/Gruss,
    Boris.

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