Open MPI logo

Open MPI User's Mailing List Archives

  |   Home   |   Support   |   FAQ   |   all Open MPI User's mailing list

Subject: Re: [OMPI users] [EXTERNAL] Re: Configuration for rendezvous and eager protocols: two-sided comm
From: Siddhartha Jana (siddharthajana24_at_[hidden])
Date: 2013-12-16 16:12:12


Noted. Thanks all for the tips !
 On 16-Dec-2013 2:36 pm, "Jeff Squyres (jsquyres)" <jsquyres_at_[hidden]>
wrote:

> Everything that Brian said, plus: note that the MCA param that Christoph
> mentioned is specifically for the "sm" (shared memory) transport. Each
> transport has their own set of MCA params (e.g., mca_btl_tcp_eager_limit,
> and friends).
>
>
> On Dec 16, 2013, at 3:19 PM, "Barrett, Brian W" <bwbarre_at_[hidden]>
> wrote:
>
> > Siddhartha -
> >
> > Christoph mentioned how to change the cross-over for shared memory, but
> it's really per-transport (so you'd have to change it for your off-node
> transport as well). That's all in the FAQ you mentioned, so hopefully you
> can take it from there. Note that, in general, moving the eager limits has
> some unintended side effects. For example, it can cause more / less
> copies. It can also greatly increase memory usage.
> >
> > Good luck,
> >
> > Brian
> >
> > On 12/16/13 1:49 AM, "Siddhartha Jana" <siddharthajana24_at_[hidden]>
> wrote:
> >
> >> Thanks Christoph.
> >> I should have looked into the FAQ section on MCA params setting @ :
> >> http://www.open-mpi.org/faq/?category=tuning#available-mca-params
> >>
> >> Thanks again,
> >> -- Siddhartha
> >>
> >>
> >> On 16 December 2013 02:41, Christoph Niethammer <niethammer_at_[hidden]>
> wrote:
> >>> Hi Siddhartha,
> >>>
> >>> MPI_Send/Recv in Open MPI implements both protocols and chooses based
> on the message size which one to use.
> >>> You can use the mca parameter "btl_sm_eager_limit" to modify the
> behaviour.
> >>>
> >>> Here the corresponding info obtained from the ompi_info tool:
> >>>
> >>> "btl_sm_eager_limit" (current value: <4096>, data source: default
> value)
> >>> Maximum size (in bytes) of "short" messages (must be >= 1)
> >>>
> >>> Regards
> >>> Christoph Niethammer
> >>>
> >>> --
> >>>
> >>> Christoph Niethammer
> >>> High Performance Computing Center Stuttgart (HLRS)
> >>> Nobelstrasse 19
> >>> 70569 Stuttgart
> >>>
> >>> Tel: ++49(0)711-685-87203
> >>> email: niethammer_at_[hidden]
> >>> http://www.hlrs.de/people/niethammer
> >>>
> >>>
> >>>
> >>> ----- Ursprüngliche Mail -----
> >>> Von: "Siddhartha Jana" <siddharthajana24_at_[hidden]>
> >>> An: "OpenMPI users mailing list" <users_at_[hidden]>
> >>> Gesendet: Samstag, 14. Dezember 2013 13:44:12
> >>> Betreff: [OMPI users] Configuration for rendezvous and eager
> protocols: two-sided comm
> >>>
> >>>
> >>>
> >>> Hi
> >>>
> >>>
> >>> In OpenMPI, are MPI_Send, MPI_Recv (and friends) implemented using
> rendezvous protocol or eager protocol?
> >>>
> >>>
> >>> If both, is there a way to choose one or the other during runtime or
> while building the library?
> >>>
> >>>
> >>> If there is a threshold of the message size that dictates the protocol
> to be used, is there a way I can alter that threshold value?
> >>>
> >>>
> >>> If different protocols were used for different versions of the library
> in the past, could someone please direct me to the exact version numbers of
> the implementations that used one or the other protocol?
> >>>
> >>>
> >>> Thanks a lot,
> >>> Siddhartha
> >>> _______________________________________________
> >>> users mailing list
> >>> users_at_[hidden]
> >>> http://www.open-mpi.org/mailman/listinfo.cgi/users
> >>> _______________________________________________
> >>> users mailing list
> >>> users_at_[hidden]
> >>> http://www.open-mpi.org/mailman/listinfo.cgi/users
> >>
> >
> >
> > --
> > Brian W. Barrett
> > Scalable System Software Group
> > Sandia National Laboratories
> > _______________________________________________
> > users mailing list
> > users_at_[hidden]
> > http://www.open-mpi.org/mailman/listinfo.cgi/users
>
>
> --
> Jeff Squyres
> jsquyres_at_[hidden]
> For corporate legal information go to:
> http://www.cisco.com/web/about/doing_business/legal/cri/
>
> _______________________________________________
> users mailing list
> users_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/users
>