[mvapich-discuss] mvapich2 slow with default mapping

[Hari Subramoni]

Hello Götz,

It looks like some sort of oversubscription is happening here. Could you
please send us the following information?

1. Output of program run after setting MV2_SHOW_CPU_BINDING=1

2. Output of ibv_devinfo executed on the system where you're seeing the
degradation.

Thanks,
Hari.
On Apr 28, 2016 10:11 AM, "Götz Waschk" <goetz.waschk at gmail.com> wrote:

> Dear Mvapich2 experts,
>
> I'm currently evaluating OpenHPC packages, including mvapich2 2.1.
> I've tested the speed using the Intel MPI benchmarks and I have
> noticed, that the first benchmark PingPong is behaving differently
> when run with 16 cores vs. 2 cores, although only two cores are in use
> and the remaining processes simply wait. The full results are in
> OpenHPC's issue tracker on github:
> https://github.com/openhpc/ohpc/issues/207#issuecomment-212319647
>
> As you can see there, the configuration change to set these variables
> helped:
>
> export MV2_SHOW_CPU_BINDING=1
> export MV2_CPU_MAPPING=0:1:2:3:4:5:6:7
>
> I still wonder why they have such an influence and the default setting
> isn't sufficient here.
>
> Regards,
> Götz Waschk
>
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