Thanks for the reply Jeff. This is directional. On 01-Feb-2014 7:51 am, "Jeff Squyres (jsquyres)" <jsquy...@cisco.com> wrote:
> On Jan 31, 2014, at 2:49 AM, Siddhartha Jana <siddharthajan...@gmail.com> > wrote: > > > Sorry for the typo: > > ** I was hoping to understand the impact of OpenMPI's implementation of > these protocols using traditional TCP. > > > > This is the paper I was referring to: > > Woodall, et al., "High Performance RDMA Protocols in HPC". > > > > > > On 31 January 2014 00:43, Siddhartha Jana <siddharthajan...@gmail.com> > wrote: > > Good evening > > Is there any documentation describing the difference in MPI-level > implementation of the eager and rendezvous protocols in OpenIB BTL versus > TCP BTL ? > > Unfortunately, there is not, sorry. Just the code. :-\ > > > I am only aware of the following paper. While this presents an excellent > overview of how RDMA capabilities of modern interconnects can be leveraged > for implementing these protocols, I was hoping to understand how OpenMPI > implications of handling these protocols using traditional TCP. > > The easiest way to think about it is that the TCP BTL could well be > implemented with just the "send" method (and no "get" or "put" methods). > > That being said, the TCP BTL does emulate the "put" method (meaning: > there's obviously no hardware support for a direct data placement using a > general socket in TCP like there is with OpenFabrics-style RDMA) simply > because it allows us to be slightly more efficient on the receiver (IIRC; > it's been a loooong time since I've looked at that code). > > -- > Jeff Squyres > jsquy...@cisco.com > For corporate legal information go to: > http://www.cisco.com/web/about/doing_business/legal/cri/ > > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users >
