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Subject: Re: [OMPI users] hwloc error in topology.c in OMPI 1.6.5
From: Ralph Castain (rhc_at_[hidden])
Date: 2014-02-28 10:11:40


On Feb 28, 2014, at 12:32 AM, Brice Goglin <Brice.Goglin_at_[hidden]> wrote:

> Le 28/02/2014 02:48, Ralph Castain a écrit :
>> Remember, hwloc doesn't actually "sense" hardware - it just parses files in the /proc area. So if something is garbled in those files, hwloc will report errors. Doesn't mean anything is wrong with the hardware at all.
>
> For the record, that's not really true:
>
> hwloc looks at /sys (and a bit /proc files), but it also uses cpuid
> instructions. 90% of the times, the former is better because the kernel
> already took care of cleaning up the hardware mess and reporting
> useful/correct info in /proc and /sys. Sometimes the kernel is too old
> and it misses some hardware quirks (like L1i sharing on Gus' machine)
> causing /sys files to be incompatible.

Fair enough - but how do you know when to probe the BIOS and when to trust what is in the file?

>
> In the end, the vast majority of problems come from buggy BIOS, and
> these cause both cpuid and kernel to report invalid info. Aside of
> upgrading the BIOS, the only solution there is to replace the topology
> with a correct XML one.
>
> Brice
>
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