Hi Ralph, OK, that certainly makes sense - so the next question is, what prevents binding memory to be local to particular cores? Is this possible in a virtualized environment like AWS HVM instances?
And does this apply only to dynamic allocations within an instance, or static as well? I'm pretty unfamiliar with how the hypervisor (KVM-based, I believe) maps out 'real' hardware, including memory, to particular instances. We've seen *some* parts of the code (bandwidth heavy) run ~10x faster on bare-metal hardware, though, *presumably* from memory locality, so it certainly has a big impact. Thanks again, and merry Christmas! - Brian On Fri, Dec 22, 2017 at 1:53 PM, r...@open-mpi.org <r...@open-mpi.org> wrote: > Actually, that message is telling you that binding to core is available, > but that we cannot bind memory to be local to that core. You can verify the > binding pattern by adding --report-bindings to your cmd line. > > > On Dec 22, 2017, at 11:58 AM, Brian Dobbins <bdobb...@gmail.com> wrote: > > > Hi all, > > We're testing a model on AWS using C4/C5 nodes and some of our timers, > in a part of the code with no communication, show really poor performance > compared to native runs. We think this is because we're not binding to a > core properly and thus not caching, and a quick 'mpirun --bind-to core > hostname' does suggest issues with this on AWS: > > *[bdobbins@head run]$ mpirun --bind-to core hostname* > > *--------------------------------------------------------------------------* > *WARNING: a request was made to bind a process. While the system* > *supports binding the process itself, at least one node does NOT* > *support binding memory to the process location.* > > * Node: head* > > *Open MPI uses the "hwloc" library to perform process and memory* > *binding. This error message means that hwloc has indicated that* > *processor binding support is not available on this machine.* > > (It also happens on compute nodes, and with real executables.) > > Does anyone know how to enforce binding to cores on AWS instances? Any > insight would be great. > > Thanks, > - Brian > _______________________________________________ > users mailing list > users@lists.open-mpi.org > https://lists.open-mpi.org/mailman/listinfo/users > > > > _______________________________________________ > users mailing list > users@lists.open-mpi.org > https://lists.open-mpi.org/mailman/listinfo/users >
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