[ET Trac] [Einstein Toolkit] #1718: MemSpeed: Re-use allocated memory

Einstein Toolkit trac-noreply at einsteintoolkit.org
Wed Jan 23 10:35:39 CST 2019

#1718: MemSpeed: Re-use allocated memory
  Reporter:  Erik Schnetter         |      Owner:  (none)
      Type:  enhancement            |     Status:  new
  Priority:  minor                  |  Milestone:
 Component:  EinsteinToolkit thorn  |    Version:  development version
Resolution:                         |   Keywords:

Comment (by Roland Haas):

 I have made a simple attempt at this and limited the amount of memory used
 (per rank) to 1GB which should be much larger than the first level of
 cache for a while still. The largest cache like memory (see
 https://en.wikipedia.org/wiki/CPU_cache#MULTILEVEL) would be the eDRAM on
 Haswell CPUs with integrated graphics which is apparently 128 MB.

 Note that this renders the {{{skip_largemem_benchmarks}}} options somewhat
 redundant, though not fully since {{{skip_largemem_benchmarks}}} would
 trigger on nodes with less than 4GB of memory per MPI rank used. It does
 become redundant on "typical" clusters though since we use only a small
 number of MPI ranks per node.

 The test still takes approximately 2min on my workstation, though at least
 1min of that is not the main memory test. This long runtime is probably a
 measure of how slow the CPUs in my workstation are is by now (certainly
 compared to the amount of memory in it).

Ticket URL: <https://trac.einsteintoolkit.org/ticket/1718#comment:4>
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