On Jul 18, 2013, at 17:12 , "Iliev, Hristo" <il...@rz.rwth-aachen.de> wrote:
> Hello, > > Could someone, who is more familiar with the architecture of the sm BTL, > comment on the technical feasibility of the following: is it possible to > easily extend the BTL (i.e. without having to rewrite it completely from > scratch) so as to be able to perform transfers using both KNEM (or other > kernel-assisted copying mechanism) for messages over a given size and the > normal user-space mechanism for smaller messages with the switch-over point > being a user-tunable parameter? This is already what the SM BTL does. When support for kernel-assisted mechanisms is enabled everything under the eager size is going over "traditional" shared memory (double copy and so on), while larger messages use the single-copy mechanism. George. > > From what I’ve seen, both implementations have something in common, e.g. both > use FIFOs to communicate controlling information. > The motivation behind this are our efforts to become greener by extracting > the best possible out of the box performance on our systems without having to > profile each and every user application that runs on them. We’ve already > determined that activating KNEM really benefits some collective operations on > big shared-memory systems, but the increased latency significantly slows down > small message transfers, which also hits the pipelined implementations. > > sm’s code doesn’t seem to be very complex but still I’ve decided to ask first > before diving any deeper. > > Kind regards, > Hristo > -- > Hristo Iliev, PhD – High Performance Computing Team > RWTH Aachen University, Center for Computing and Communication > Rechen- und Kommunikationszentrum der RWTH Aachen > Seffenter Weg 23, D 52074 Aachen (Germany) > > > _______________________________________________ > devel mailing list > de...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/devel
