My understanding, having looked at the code for this, is that no thread binding is set. The OS will hopefully do the right thing when the cores are undersubscribed, but I see no thread affinity code in the MPICH source for the comm threads. MVAPICH has some additional (i.e. non-MPICH) affinity code but I think it is mostly for process-binding. I have a modified version of MPICH that allows the user to set the affinity of the comm threads explicitly. I was interested in pinning all of the comm threads to one core and letting them fight for time. For example, on an 8-core node, I was hoping to get async progress on 7 processes by pinning 7 comm threads to the 8th core. My patches for setting comm thread affinity are pretty simple. I assume you want me to share them? Jeff On Sat, Feb 23, 2013 at 6:23 PM, Jed Brown <[email protected]> wrote:

Do the Hydra affinity settings apply to the internal comm thread created using MPICH_ASYNC_PROGRESS? Is there a way to set affinity for the comm threads so that they do not compete with application threads?

http://wiki.mpich.org/mpich/index.php/Using_the_Hydra_Process_Manager#Proces...

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-- Jeff Hammond Argonne Leadership Computing Facility University of Chicago Computation Institute [email protected] / (630) 252-5381 http://www.linkedin.com/in/jeffhammond https://wiki.alcf.anl.gov/parts/index.php/User:Jhammond