Jeff Squyres wrote:
>With Mellanox's new HCA (ConnectX), extremely low latencies are
>possible for short messages between two MPI processes. Currently,
>OMPI's latency is around 1.9us while all other MPI's (HP MPI, Intel
>MPI, MVAPICH, etc.) are around 1.4us. A big reason for this
>difference is that, at least with MVAPICH, they are doing wire
>protocol header caching where the openib BTL does not. Specifically:
>- Mellanox tested MVAPICH with the header caching; latency was around
>- Mellanox tested MVAPICH without the header caching; latency was
>Given that OMPI is the lone outlier around 1.9us, I think we have no
>choice except to implement the header caching and/or examine our
>header to see if we can shrink it. Mellanox has volunteered to
>implement header caching in the openib btl.
>Any objections? We can discuss what approaches we want to take
>(there's going to be some complications because of the PML driver,
>etc.); perhaps in the Tuesday Mellanox teleconf...?
This sounds great. Sun, would like to hear how thing are being done
so we can possibly port the solution to the udapl btl.