[openib-general] IB MTU tunable for uDAPL and/or Intel MPI?

[Arlin Davis]

Scott Weitzenkamp (sweitzen) wrote:

> While we're talking about MTUs, is the IB MTU tunable in uDAPL and/or 
> Intel MPI via env var or config file?
>  
> Looks like Intel MPI 2.0.1 uses 2K for IB MTU like MVAPICH does in 
> OFED 1.0 rc4 and rc6, I'd like to try 1K with Intel MPI.
>  
> Scott


There is no mechanism for me to modify the MTU using rdma_cm so whatever 
is returned in the path record is what you get with the OpenIB-cma 
provider. However, you could use the OpenIB-scm provider which is hard 
coded for 1K MTU as a comparision.  Can you run with "-genv 
I_MPI_DAPL_PROVIDER OpenIB-scm" on your cluster?

-arlin

>
>     ------------------------------------------------------------------------
>     *From:* openib-general-bounces at openib.org
>     [mailto:openib-general-bounces at openib.org] *On Behalf Of *Scott
>     Weitzenkamp (sweitzen)
>     *Sent:* Thursday, June 08, 2006 4:38 PM
>     *To:* Tziporet Koren; openfabrics-ewg at openib.org
>     *Cc:* openib-general
>     *Subject:* RE: [openib-general] OFED-1.0-rc6 is available
>
>     The MTU change undos the changes for bug 81, so I have reopened
>     bug 81 (http://openib.org/bugzilla/show_bug.cgi?id=81).
>      
>     With rc6, PCI-X osu_bw and osu_bibw performance is bad, and PCI-E
>     osu_bibw performance is bad.  I've enclosed some performance data,
>     look at rc4 vs rc5 vs rc6 for Cougar/Cheetah/LionMini.
>      
>     Are there other benchmarks driving the changes in rc6 (and rc4)?
>      
>     Scott Weitzenkamp
>     SQA and Release Manager
>     Server Virtualization Business Unit
>     Cisco Systems
>      
>
>          
>
>         *OSU MPI:*
>
>         ·        Added mpi_alltoall fine tuning parameters
>
>         ·        Added default configuration/documentation file
>         $MPIHOME/etc/mvapich.conf
>
>         ·        Added shell configuration files 
>         $MPIHOME/etc/mvapich.csh , $MPIHOME/etc/mvapich.csh
>
>         ·        Default MTU was changed back to 2K for InfiniHost III
>         Ex and InfiniHost III Lx HCAs. For InfiniHost card recommended
>         value is:
>         VIADEV_DEFAULT_MTU=MTU1024
>
>------------------------------------------------------------------------
>
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