<div dir="ltr">There is an FAQ entry on this topic, but it isn't named in a way that would have made it easy for you to find. <a href="https://wiki.mpich.org/mpich/index.php/Frequently_Asked_Questions#Q:_Why_does_my_MPI_program_run_much_slower_when_I_use_more_processes.3F">https://wiki.mpich.org/mpich/index.php/Frequently_Asked_Questions#Q:_Why_does_my_MPI_program_run_much_slower_when_I_use_more_processes.3F</a><div><br></div><div>While ch3:sock is deprecated, I believe the PETSc team uses it on a regular basis, so it should work for common MPI operations.<br><div><br></div><div>It seems that libfabric supports efficient waiting (<a href="https://ofiwg.github.io/libfabric/v1.10.0/man/fabtests.7.html">https://ofiwg.github.io/libfabric/v1.10.0/man/fabtests.7.html</a>) but I have no idea if or how this would work inside of MPICH.</div><div><br></div><div><div>MPICH-derived and ABI-compatible Intel MPI supports wait backoff options, although I have never used them. <a href="https://software.intel.com/en-us/forums/intel-clusters-and-hpc-technology/topic/806493">https://software.intel.com/en-us/forums/intel-clusters-and-hpc-technology/topic/806493</a><br></div></div><div><br></div><div>You can install Intel MPI with Apt for zero cost. <a href="https://software.intel.com/content/www/us/en/develop/articles/installing-intel-parallel-studio-xe-runtime-2019-using-apt-repository.html">https://software.intel.com/content/www/us/en/develop/articles/installing-intel-parallel-studio-xe-runtime-2019-using-apt-repository.html</a> </div><div><br></div><div>Best,<br></div><div><br></div><div>Jeff (who works for Intel)</div></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Jun 3, 2020 at 1:57 PM Mccall, Kurt E. (MSFC-EV41) via discuss <<a href="mailto:discuss@mpich.org">discuss@mpich.org</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<p class="MsoNormal">Is there a means to tell MPICH to yield to other processes when performing a busy-wait for incoming messages? The page below distinguishes between “aggressive busy-wait” and “degraded busy-wait”, where the latter is what I’d like to try.<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal"><a href="https://stackoverflow.com/questions/14560714/probe-seems-to-consume-the-cpu/14562840#14562840" target="_blank">https://stackoverflow.com/questions/14560714/probe-seems-to-consume-the-cpu/14562840#14562840</a><u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Thanks,<u></u><u></u></p>
<p class="MsoNormal">Kurt<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
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</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature">Jeff Hammond<br><a href="mailto:jeff.science@gmail.com" target="_blank">jeff.science@gmail.com</a><br><a href="http://jeffhammond.github.io/" target="_blank">http://jeffhammond.github.io/</a></div>