Open MPI logo

Hardware Locality Development Mailing List Archives

  |   Home   |   Support   |   FAQ   |   all Hardware Locality Development mailing list

Subject: Re: [hwloc-devel] hwloc_distances as utility?
From: Jiri Hladky (hladky.jiri_at_[hidden])
Date: 2011-07-05 16:04:45


Hi Brice,

> By the way, lstopo shows distance information, but it does not change it
> depending on -l/-p. We may want to fix this.
>

Thanks for the hint, I din't know it.

> Actually, Linux only uses the number of hops on one specific MIPS
> architecture (SGI IP27 Origin 200/2000). In other cases, it uses the
> cpu-to-memory latency (usually reported by ACPI or so).
>

Well, this is interesting. numactl --hardware shows the number of hops,
regarding to the information from that private BZ. Where does hwloc takes
the distance information? Is it stored with

hwloc-gather-topology

script? If yes, could me send me the output of hwloc-gather-topology for
some NUMA box? I don't have access to any NUMA running a recent version of
kernel.

>
> > On some systems number of hops does not represent memory bandwidth. I
> > have reported this in BZ 655041
> >
> > https://bugzilla.redhat.com/show_bug.cgi?id=655041
>
> This bug is private unfortunately.
>
> > In any case I believe that hwloc-report-instances would be useful
> > utility. Please let me know your opinion.
>
> Agreed.
>

OK, I will try to implement it as time permits.

Thanks
Jirka