Should we replace OMPI's use of sched_yield() with usleep()? David -- could you try replacing the call to sched_yield() in opal/runtime/opal_progress.c (somewhere around line 220) to usleep(1) and see if that gives the behavior that you want (without twonking a /proc value)? You might also have to add "#include <unistd.h>" at the top of the file.
On Jul 22, 2010, at 12:03 PM, David Ronis wrote: > That did it. Thanks. > > David > > On Wed, 2010-07-21 at 15:29 -0500, Dave Goodell wrote: > > On Jul 21, 2010, at 2:54 PM CDT, Jed Brown wrote: > > > > > On Wed, 21 Jul 2010 15:20:24 -0400, David Ronis <david.ro...@mcgill.ca> > > > wrote: > > >> Hi Jed, > > >> > > >> Thanks for the reply and suggestion. I tried adding -mca > > >> yield_when_idle 1 (and later mpi_yield_when_idle 1 which is what > > >> ompi_info reports the variable as) but it seems to have had 0 effect. > > >> My master goes into fftw planning routines for a minute or so (I see the > > >> threads being created), but the overall usage of the slaves remains > > >> close to 100% during this time. Just to be sure, I put the slaves into > > >> a MPI_Barrier(MPI_COMM_WORLD) while they were waiting for the fftw > > >> planner to finish. It also didn't help. > > > > > > They still spin (instead of using e.g. select()), but call sched_yield() > > > so should only be actively spinning when nothing else is trying to run. > > > Are you sure that the planner is always running in parallel? What OS > > > and OMPI version are you using? > > > > sched_yield doesn't work as expected in late 2.6 Linux kernels: > > http://kerneltrap.org/Linux/CFS_and_sched_yield > > > > If this scheduling behavior change is affecting you, you might be able to > > fix it with: > > > > echo "1" >/proc/sys/kernel/sched_compat_yield > > > > -Dave > > > > > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users > -- Jeff Squyres jsquy...@cisco.com For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/
