On 14:25 Thu 08 Dec , Dave Love wrote: > Jeff Hammond <jeff.scie...@gmail.com> writes: > > >> > >> > >> > Note that MPI implementations may be interested in taking advantage of > >> > https://software.intel.com/en-us/blogs/2016/10/06/intel- > >> xeon-phi-product-family-x200-knl-user-mode-ring-3-monitor-and-mwait. > >> > >> Is that really useful if it's KNL-specific and MSR-based, with a setup > >> that implementations couldn't assume? > >> > >> > > Why wouldn't it be useful in the context of a parallel runtime system like > > MPI? MPI implementations take advantage of all sorts of stuff that needs > > to be queried with configuration, during compilation or at runtime. > > I probably should have said "useful in practice". The difference from > other things I can think of is that access to MSRs is privileged, and > it's not clear to me what the implications are of changing it or to what > extent you can assume people will. > > > TSX requires that one check the CPUID bits for it, and plenty of folks are > > happily using MSRs (e.g. > > http://www.brendangregg.com/blog/2014-09-15/the-msrs-of-ec2.html). > > Yes, as root, and there are N different systems to at least provide > unprivileged read access on HPC systems, but that's a bit different, I > think.
LIKWID[1] uses a daemon to provide limited RW access to MSRs for applications. I wouldn't wonder if support for this was added to LIKWID by RRZE. Cheers -Andreas [1] https://github.com/RRZE-HPC/likwid -- ========================================================== Andreas Schäfer HPC and Supercomputing Institute for Multiscale Simulation Friedrich-Alexander-Universität Erlangen-Nürnberg, Germany +49 9131 85-20866 PGP/GPG key via keyserver http://www.libgeodecomp.org ========================================================== (\___/) (+'.'+) (")_(") This is Bunny. Copy and paste Bunny into your signature to help him gain world domination!
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