Re: Off topic: Numactl "distance" wrong

From: Cliff Wickman
Date: Fri Apr 03 2009 - 17:01:17 EST


On Fri, Apr 03, 2009 at 01:49:27PM -0700, Yinghai Lu wrote:
> On Fri, Apr 3, 2009 at 1:16 PM, Brice Goglin <Brice.Goglin@xxxxxxxx> 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?

numactl and libnuma are discussed on
linux-numa@xxxxxxxxxxxxxxx

> >>
> >
> > 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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--
Cliff Wickman
Silicon Graphics, Inc.
cpw@xxxxxxx
(651) 683-3824
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