linux-kernel - Re: [PATCH] x86_64: make amd quad core 8 socket system not be clustered

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Date:	Tue, 26 Feb 2008 15:31:11 -0800
From:	Ravikiran Thirumalai <kiran@...lemp.com>
To:	Yinghai Lu <yhlu.kernel@...il.com>
Cc:	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	shai@...lemp.com
Subject: Re: [PATCH] x86_64: make amd quad core 8 socket system not be clustered_box v2

On Tue, Feb 26, 2008 at 03:16:16PM -0800, Yinghai Lu wrote:
>On Tue, Feb 26, 2008 at 1:24 PM, Ravikiran Thirumalai <kiran@...lemp.com> wrote:
>>
>> On Tue, Feb 26, 2008 at 01:10:57PM -0800, Yinghai Lu wrote:
>>  >On Tue, Feb 26, 2008 at 12:32 PM, Ravikiran Thirumalai
>>  ><kiran@...lemp.com> wrote:
>>  >> On Tue, Feb 26, 2008 at 11:00:58AM -0800, Yinghai Lu wrote:
>>  >>  >
>>  >>  >1. if acpi=off ?
>>  >>
>>  >>  Well that is not a realistic scenario for any multi chassi NUMA machine,
>>  >>  since the proximity information is very important and turning acpi off
>>  >>  deprives the OS of this information.
>>  >
>>  >actually OS should detect the distance instead of rely on SLIT.
>>
>>  How does it do that?  ACPI SRAT is needed to determine this, and it wouldn't
>>  work if acpi=off.
>
>srat only have apicid to node mapping, and ram to node mapping.

Which is very important for performance.

>
>for amd64 system, when acpi=off
>ram to node mapping can be retrieved from pci conf space

I was referring to all types of numa systems, not just AMD.  The pci config
space is amd specific.  Multi chassi systems in particular would be
acpi SRAT based.  Anyways.

Kiran
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