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Subject: Re: [hwloc-users] lstopo and GPus
From: Brice Goglin (Brice.Goglin_at_[hidden])
Date: 2012-08-28 08:43:19


Le 28/08/2012 14:23, Samuel Thibault a écrit :
> Gabriele Fatigati, le Tue 28 Aug 2012 14:19:44 +0200, a écrit :
>> I'm using hwloc 1.5. I would to see how GPUs are connected with the processor
>> socket using lstopo command.
> About connexion with the socket, there is indeed no real graphical
> difference between "connected to socket #1" and "connected to all
> sockets". You can use the text output for that:
>
> $ lstopo
> Socket #0
> Socket #1
> PCI...
> (connected to socket #1)
>
> vs
>
> $ lstopo
> Socket #0
> Socket #1
> PCI...
> (connected to both sockets)

Fortunately, this won't occur in most cases (including Gabriele's
machines) because there's a NUMAnode object above each socket. Both the
socket and the PCI bus are drawn inside the NUMA box, so things appear
OK in graphics to.

I've never seen the problem on a real machine, but a fake topology with
a PCI bus attached to a socket that is not strictly equal to the above
NUMA node is indeed wrongly displayed.

Gabriele, assuming you have a dual Xeon X56xx Westmere machine, there
are plenty of such platforms where the GPU is indeed connected to both
sockets. Or it could be a buggy BIOS.

Brice