issue with resource management on KNL

Issue #320 new
Jonas Thies
created an issue

when running a ghost example (e.g. the spmv_bench from ghost-apps or a phist Driver) on our KNL System I get single core Performance only. @Dominik Ernst, @christiealappatt, does this work for you? Can you also try compiling phist+ghost and running e.g. phist_bench_stream?

GHOST correctly reports 68 cores and I explicitly set OMP_NUM_THREADS=64, but in 'top' I see 100% CPU usage instead of ~6400%.

I think it is important that this works well 'out-of-the-box' for People who try it on a KNL.

Comments (2)

  1. Dominik Ernst

    For benchmarks on KNL sofar I did not have to set the number of Cores to use. I ran spmv_bench on our KNL machine with:

    numactl -m 1 ./spmvbench -f SELL-32-1 -m Topi-128-128-128 -i 2000 -R 1

    which resulted in 82-86 GFlop/s, which is more than single core performance. There is a lot of variance in the result though. In top I do see 25600% cpu usage. I had to set the number of iterations to a large value though, because otherwise the spmv is only a tiny fraction of the execution time, and it is impossible to see in top. The rest of the execution shows just 100% usage.

    I tried to compile phist on our KNL machine, but the newer required CMake version is broken on this machine.

  2. Jonas Thies reporter

    thanks for the hint, I also saw more CPU usage in top when doing more iterations, and got about 30 GFlop/s for a graphene Matrix in the ghost-apps. I will recompile phist and see if I get similar results from within phist.

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