linux-kernel - Re: Off topic: Numactl "distance" wrong

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Message-ID: <20090407075908.GL17934@one.firstfloor.org>
Date:	Tue, 7 Apr 2009 09:59:08 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Brice Goglin <Brice.Goglin@...ia.fr>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Yinghai Lu <yhlu.kernel@...il.com>,
	Chris Worley <worleys@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: Off topic: Numactl "distance" wrong

On Tue, Apr 07, 2009 at 12:44:21AM -0700, David Rientjes wrote:
> On Tue, 7 Apr 2009, Andi Kleen wrote:
> 
> > I'm not aware of any that does. In general applications usually
> > only use the bare basics of NUMA API (if at all), the fancy stuff tends
> > to be more slideware.
> > 
> > If it's true then the correct place would be to fix the BIOS.
> > 
> 
> We already verify that each node has local distance to itself and that its 
> distance to any other node is greater than local when determining whether 
> the SLIT is valid.
> 
> It would also be possible to verify that the distance between two 
> localities is described consistently in the table (like in the following 
> patch).

Do you have an real-world example where this is wrong? 

> 
> I do think it would be helpful to add an acpi=noslit option, however, that 
> would disable parsing the SLIT if it is known to incorrectly describe the 
> physical topology of the system.

The check heuristic handles this. I am not aware of a case where it really
fails and let's something really bogus through.

In general this thread seems to contain much more speculation than
facts.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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