Hi, It is v1.2, default configuration. If it matters: OS is RHEL (2.6.9-42.0.3.ELsmp) on x86_64.
I have noticed this for 2 apps so far, mpiBLAST and HPL, which are both course grained. Thanks, Todd On 3/22/07 2:38 PM, "Ralph Castain" <r...@lanl.gov> wrote: > > > > On 3/22/07 11:30 AM, "Heywood, Todd" <heyw...@cshl.edu> wrote: > >> Ralph, >> >> Well, according to the FAQ, aggressive mode can be "forced" so I did try >> setting OMPI_MCA_mpi_yield_when_idle=0 before running. I also tried turning >> processor/memory affinity on. Efffects were minor. The MPI tasks still cycle >> bewteen run and sleep states, driving up system time well over user time. > > Yes, that's true - and we do (should) respect any such directive. > >> >> Mpstat shows SGE is indeed giving 4 or 2 slots per node as approporiate >> (depending on memory) and the MPI tasks are using 4 or 2 cores, but to be >> sure, I also tried running directly with a hostfile with slots=4 or slots=2. >> The same behavior occurs. > > Okay - thanks for trying that! > >> >> This behavior is a function of the size of the job. I.e. As I scale from 200 >> to 800 tasks the run/sleep cycling increases, so that system time grows from >> maybe half the user time to maybe 5 times user time. >> >> This is for TCP/gigE. > > What version of OpenMPI are you using? This sounds like something we need to > investigate. > > Thanks for the help! > Ralph > >> >> Todd >> >> >> On 3/22/07 12:19 PM, "Ralph Castain" <r...@lanl.gov> wrote: >> >>> Just for clarification: ompi_info only shows the *default* value of the MCA >>> parameter. In this case, mpi_yield_when_idle defaults to aggressive, but >>> that value is reset internally if the system sees an "oversubscribed" >>> condition. >>> >>> The issue here isn't how many cores are on the node, but rather how many >>> were specifically allocated to this job. If the allocation wasn't at least 2 >>> (in your example), then we would automatically reset mpi_yield_when_idle to >>> be non-aggressive, regardless of how many cores are actually on the node. >>> >>> Ralph >>> >>> >>> On 3/22/07 7:14 AM, "Heywood, Todd" <heyw...@cshl.edu> wrote: >>> >>>> Yes, I'm using SGE. I also just noticed that when 2 tasks/slots run on a >>>> 4-core node, the 2 tasks are still cycling between run and sleep, with >>>> higher system time than user time. >>>> >>>> Ompi_info shows the MCA parameter mpi_yield_when_idle to be 0 (aggressive), >>>> so that suggests the tasks aren't swapping out on bloccking calls. >>>> >>>> Still puzzled. >>>> >>>> Thanks, >>>> Todd >>>> >>>> >>>> On 3/22/07 7:36 AM, "Jeff Squyres" <jsquy...@cisco.com> wrote: >>>> >>>>> Are you using a scheduler on your system? >>>>> >>>>> More specifically, does Open MPI know that you have for process slots >>>>> on each node? If you are using a hostfile and didn't specify >>>>> "slots=4" for each host, Open MPI will think that it's >>>>> oversubscribing and will therefore call sched_yield() in the depths >>>>> of its progress engine. >>>>> >>>>> >>>>> On Mar 21, 2007, at 5:08 PM, Heywood, Todd wrote: >>>>> >>>>>> P.s. I should have said this this is a pretty course-grained >>>>>> application, >>>>>> and netstat doesn't show much communication going on (except in >>>>>> stages). >>>>>> >>>>>> >>>>>> On 3/21/07 4:21 PM, "Heywood, Todd" <heyw...@cshl.edu> wrote: >>>>>> >>>>>>> I noticed that my OpenMPI processes are using larger amounts of >>>>>>> system time >>>>>>> than user time (via vmstat, top). I'm running on dual-core, dual-CPU >>>>>>> Opterons, with 4 slots per node, where the program has the nodes to >>>>>>> themselves. A closer look showed that they are constantly >>>>>>> switching between >>>>>>> run and sleep states with 4-8 page faults per second. >>>>>>> >>>>>>> Why would this be? It doesn't happen with 4 sequential jobs >>>>>>> running on a >>>>>>> node, where I get 99% user time, maybe 1% system time. >>>>>>> >>>>>>> The processes have plenty of memory. This behavior occurs whether >>>>>>> I use >>>>>>> processor/memory affinity or not (there is no oversubscription). >>>>>>> >>>>>>> Thanks, >>>>>>> >>>>>>> Todd >>>>>>> >>>>>>> _______________________________________________ >>>>>>> users mailing list >>>>>>> us...@open-mpi.org >>>>>>> http://www.open-mpi.org/mailman/listinfo.cgi/users >>>>>> >>>>>> _______________________________________________ >>>>>> users mailing list >>>>>> us...@open-mpi.org >>>>>> http://www.open-mpi.org/mailman/listinfo.cgi/users >>>>> >>>> >>>> _______________________________________________ >>>> users mailing list >>>> us...@open-mpi.org >>>> http://www.open-mpi.org/mailman/listinfo.cgi/users >>> >>> >>> _______________________________________________ >>> users mailing list >>> us...@open-mpi.org >>> http://www.open-mpi.org/mailman/listinfo.cgi/users >> >> _______________________________________________ >> users mailing list >> us...@open-mpi.org >> http://www.open-mpi.org/mailman/listinfo.cgi/users > > > _______________________________________________ > users mailing list > us...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/users
