[lug] Processor assignment

Rob Nagler nagler at bivio.biz
Wed Mar 30 15:49:03 MDT 2016


We are using OpenMPI to distribute a job across many cores, but the kernel
isn't cooperating. It overloads cores when there are many available cores.
At first, we thought this only showed up in Docker containers, but we've
been able to reproduce it natively both on CentOS 6 and Fedora 23 and with
Docker on CentOS 6, Fedora 23, and Debian Jessie.

A simple example program along with a short description can be found here:
https://github.com/robnagler/mpi-play/issues/1  On a 2 x E5-2699-v3 node
running Debian, we're seeing proper allocation natively but in the
container, the allocation is "incorrect".

For the tl;dr history (including the Docker rabbit hole), look at this:
https://github.com/radiasoft/devops/issues/13

Any ideas or pointers to where I could get help would be greatly
appreciated.

Thanks,
Rob
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