Hi Ralph, The Mac OS X affinity stuff doesn't work like Linux, etc. The document I pointed to is sparse in details, but basically they didn't leave a way for unrelated processes to affect how they are scheduled relative to each other. Only processes/threads that have a fork/thread-spawn ancestor can cooperate/coordinate on who runs where.
They have this "affinity namespace" thing that would need to be inherited from a common ancestor, so that then each rank could specify within that namespace which other threads it should/should-not share L2 cache's with. Its funky, and not at all like how we currently do affinity. That was why I said this would be "quite a bit of work". It is probably not worth the effort, unless Apple wanted to contribute directly. On Fri, Dec 12, 2008 at 11:29 AM, Ralph Castain <r...@lanl.gov> wrote: > But we don't want the child to inherit affinity from the orted anyway, so I > don't see why the exec call is an issue for us. The MPI proc sets its own > affinity during MPI_Init using the paffinity framework, so it looks to me > like the only thing missing is the correct set_affinity code in the darwin > paffinity module. > > > On Dec 12, 2008, at 9:21 AM, Tim Mattox wrote: > >> Hello, >> I just ran across this document from Apple that describes >> the Thread affinity scheme that was added in Leopard. >> http://developer.apple.com/releasenotes/Performance/RN-AffinityAPI/ >> >> In its current form, and how orteds start the MPI ranks with exec, >> we can't use this, AFAIK. However, if someone cares, there >> might be a path for doing MPI process affinity on Mac OS X >> with quite a bit of work. Let me know if you have the >> time & interest, and I can explain my idea on how to do it. >> >> For the curious, here is the key text extracted from that document: >> "Generally, the affinity tag namespace is private to one task >> (process). However, a child process forked after its parent has made a >> THREAD_AFFINITY_POLICY call will share the affinity namespace of the >> parent process. This enables a family of forked processes to share an >> affinity namespace despite comprising separate tasks. Moreover, the >> forked child inherits the affinity tag of its parent. Hence, a parent >> can seed a number of child processes within an arbitrary organization >> of shared affinity sets. Note: affinity namespace inheritance is >> destroyed by the exec(3) system call, however." >> >> It's that last sentence about exec(3) that makes things (very) difficult >> for us. >> -- >> Tim Mattox, Ph.D. - http://homepage.mac.com/tmattox/ >> tmat...@gmail.com || timat...@open-mpi.org >> I'm a bright... http://www.the-brights.net/ >> _______________________________________________ >> devel mailing list >> de...@open-mpi.org >> http://www.open-mpi.org/mailman/listinfo.cgi/devel > > _______________________________________________ > devel mailing list > de...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/devel > -- Tim Mattox, Ph.D. - http://homepage.mac.com/tmattox/ tmat...@gmail.com || timat...@open-mpi.org I'm a bright... http://www.the-brights.net/
