linux-kernel - Re: [PATCH] [arch-x86] Allow SRAT integrity check to be skipped

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Message-ID: <20100902065731.GB29972@elte.hu>
Date:	Thu, 2 Sep 2010 08:57:31 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@...el.com>
Cc:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	x86@...nel.org, linux-kernel@...r.kernel.org, andi@...stfloor.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH] [arch-x86] Allow SRAT integrity check to be skipped


* Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@...el.com> wrote:

> On certain BIOSes, SRAT enumeration isn't exported correctly. This 
> leads to NUMA node enumeration failure, and causes the kernel to fall 
> back onto a single node treated as flat memory.  This can happen on 
> large, multi-socket systems (4 or more sockets), and becomes 
> problematic for performance.
> 
> This patch adds a boot parameter to allow a kernel to be booted with 
> the option to skip the SRAT check.  There are BIOSes in production 
> that have these failures, so this will allow people in the field to 
> work around these BIOS issues.

> + 	sratbypassbios
> +		If specified, will skip an SRAT check for PXM coverage
> +		from BIOS enumeration.  Only to be used on systems with
> +		buggy BIOSes that munge the SRAT enumeration.

This isnt a particularly useful solution to users of said systems - they 
have to figure out that this option exists, and then they have to enter 
this option on the boot line.

A better solution would be to match these systems using DMI filters - 
_and_ to also have the boot time option to cover the case where a new 
system comes out with such a breakage. (or there's some system not yet 
mapped)


	Ingo
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