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Subject: Re: [hwloc-users] AMD Opteron 6238 lstopo wrong topology
From: Petros Aristidou (p3tris_at_[hidden])
Date: 2012-04-19 08:29:51


Thanks both for the fast response! I upgraded to 3.2 kernel from the
unstable and now I get the right ones:
http://dl.dropbox.com/u/258337/lstop_odysseus_1.4.1_kernel3.2.pdf

I generally like to stick with Debian stable because I never got any
problem. While with unstable or Ubuntu I get some not so pleasant glitches
from time to time.

Thanks a lot!

Petros

On Thu, Apr 19, 2012 at 14:05, Brice Goglin <Brice.Goglin_at_[hidden]> wrote:

> Hello,
>
> This is a longstanding kernel bug. It was finally fixed recently in kernel
> 3.3 and backported in 3.2.9 and 3.0.23. Not sure if the Debian kernel devs
> would accept backporting it to squeeze. The relevant commit is.
>
> commit 32c3233885eb10ac9cb9410f2f8cd64b8df2b2a1
> Author: Andreas Herrmann <andreas.herrmann3_at_[hidden]> <andreas.herrmann3_at_[hidden]>
> Date: Wed Feb 8 20:52:29 2012 +0100
>
> x86/amd: Fix L1i and L2 cache sharing information for AMD family 15h processors
>
> For L1 instruction cache and L2 cache the shared CPU information
> is wrong. On current AMD family 15h CPUs those caches are shared
> between both cores of a compute unit.
>
> This fixes https://bugzilla.kernel.org/show_bug.cgi?id=42607
>
>
> If you need to stay with an old kernel that can't be fixed for this
> machine, we can provide you with a corrected XML topology.
>
> Brice
>
>
>
>
> On 19/04/2012 13:51, Petros Aristidou wrote:
>
> Hi everyone,
>
> I run lstopo on my 4-socket 6238, Supermicro system and I get the
> following figures: http://dl.dropbox.com/u/258337/lstop_odysseus_1.4.1.pdfand
> http://dl.dropbox.com/u/258337/lstopo_verbose.txt
>
> It shows that each socket has 2 numanodes with 6 cores each. It shows a
> shared L3 memory but dedicated L2 and L1. In other references, like:
>
> http://www.olcf.ornl.gov/wp-content/uploads/2012/01/TitanWorkshop2012_Day1_AMD.pdf
> http://www.siliconmechanics.com/files/BulldozerInterlagosInfo.pdf and
> http://www.hpc2n.umu.se/resources/abisko/cpuarch
> I get that L1 is dedicated, L2 is shared by 2 cores and L3 shared by all 6
> in the numanode.
>
> What's the truth? Is lstopo wrongly reporting that?
>
> I am running the latest stable version of Debian Linux (6.0.4 Squeeze)
> with all updates and have hwloc v1.4.1 installed.
>
> Any insight is welcome!
>
> Petros
>
>
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