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

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Message-ID: <86802c440904031349v31f84f8anf082db7505e60387@mail.gmail.com>
Date:	Fri, 3 Apr 2009 13:49:27 -0700
From:	Yinghai Lu <yhlu.kernel@...il.com>
To:	Brice Goglin <Brice.Goglin@...ia.fr>
Cc:	Chris Worley <worleys@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: Off topic: Numactl "distance" wrong

On Fri, Apr 3, 2009 at 1:16 PM, Brice Goglin <Brice.Goglin@...ia.fr> wrote:
> Chris Worley wrote:
>> Sorry for an off topic, but I'm hoping somebody can point me in the
>> right direction of where to direct this question...
>>
>> I have an Opteron system where I've seen the HW diagrams, and each of
>> 4 sockets is directly connected (HT) to two other sockets, and two HT
>> hops away from a third (i.e. a simple square topology, no X in the
>> middle).
>>
>> Yet, "numactl --hardware" shows but one hop to each socket:
>>
>> # numactl --hardware
>> ...
>> node   0   1   2   3
>>   0:  10  20  20  20
>>   1:  20  10  20  20
>>   2:  20  20  10  20
>>   3:  20  20  20  10
>>
>> I know this is wrong.
>>
>> Who would be the right person (or list) to talk about this?
>>
>
> IIRC, the motherboard/BIOS is supposed to report numa distances through
> the PXM ACPI method. But I have never seen any opteron box do it
> properly. So you just get 10 for "local" and 20 for "remote". Some
> Itanium machines however report actual distances.

for x86 64 bit, we are copying SLIT table and save another copy.

could provide one /sys interface to make user could modify it...

YH
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