[ET Trac] [Einstein Toolkit] #1850: Severe performance problem on Stampede

Einstein Toolkit trac-noreply at einsteintoolkit.org
Mon Mar 21 10:19:20 CDT 2016

#1850: Severe performance problem on Stampede
  Reporter:  hinder      |       Owner:                     
      Type:  defect      |      Status:  confirmed          
  Priority:  major       |   Milestone:                     
 Component:  SimFactory  |     Version:  development version
Resolution:              |    Keywords:                     

Comment (by hinder):

 The tacc_affinity script is recommended for stampede
 (https://portal.xsede.org/tacc-stampede).  It is supposed to guarantee
 that the processes are distributed among sockets, as well as the memory
 they allocate. We already use this in the simfactory run script.  This is
 the only place that this can be done, because once Cactus has started, MPI
 has already initialised itself, and may have allocated memory on the wrong
 socket if the process has not yet been pinned to a socket.

 Erik has indicated that the KMP_AFFINITY setting is likely only correct
 when you have only a single process per node, and using this variable
 cannot be correct when you have more than one process per node, because
 the compiler, which interprets this variable, does not know about the
 additional processes.  I observed that removing the setting of this
 variable eliminated the performance problem that I saw when not using
 SystemTopology.  I therefore propose that the setting of this variable is
 removed from the run script.

Ticket URL: <https://trac.einsteintoolkit.org/ticket/1850#comment:22>
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