devel-boun...@open-mpi.org wrote on 08/29/2011 04:20:30 PM: > De : Ralph Castain <r...@open-mpi.org> > A : Open MPI Developers <de...@open-mpi.org> > Date : 08/29/2011 04:26 PM > Objet : Re: [OMPI devel] known limitation or bug in hwloc? > Envoyé par : devel-boun...@open-mpi.org > > Actually, I'll eat those words. I was looking at the wrong place. > > Yes, that is a bug in hwloc. It needs to loop over CPU_MAX for those > cases where the bit mask extends over multiple words.
But I'm afraid the fix won't be trivial at all: hwloc in itself is coherent: it loops overs NUM_BITS, but it uses masks that are NUM_BITS wide (hwloc_bitmap_t set)... Regards, Nadia > > > On Aug 29, 2011, at 7:16 AM, Ralph Castain wrote: > > > Actually, if you look closely at the definition of those two > values, you'll see that it really doesn't matter which one we loop > over. The NUM_BITS value defines the actual total number of bits in > the mask. The CPU_MAX is the total number of cpus we can support, > which was set to a value such that the two are equal (i.e., it's a > power of two that happens to be an integer multiple of 64). > > > > I believe the original intent was to allow CPU_MAX to be > independent of address-alignment questions, so NUM_BITS could > technically be greater than CPU_MAX. Even if this happens, though, > all that would do is cause the loop to run across more bits than required. > > > > So it doesn't introduce a limitation at all. In hindsight, we > could simplify things by eliminating one of those values and just > putting a requirement on the number that it be a multiple of 64 so > it aligns with a memory address. > > > > > > On Aug 29, 2011, at 7:05 AM, Kenneth Lloyd wrote: > > > >> Nadia, > >> > >> Interesting. I haven't tried pushing this to levels above 8 on a particular > >> machine. Do you think that the cpuset / paffinity / hwloc only applies at > >> the machine level, at which time you need to employ a graph with carto? > >> > >> Regards, > >> > >> Ken > >> > >> -----Original Message----- > >> From: devel-boun...@open-mpi.org [mailto:devel-boun...@open-mpi.org] On > >> Behalf Of nadia.derbey > >> Sent: Monday, August 29, 2011 5:45 AM > >> To: Open MPI Developers > >> Subject: [OMPI devel] known limitation or bug in hwloc? > >> > >> Hi list, > >> > >> I'm hitting a limitation with paffinity/hwloc with cpu numbers >= 64. > >> > >> In opal/mca/paffinity/hwloc/paffinity_hwloc_module.c, module_set() is > >> the routine that sets the calling process affinity to the mask given as > >> parameter. Note that "mask" is a opal_paffinity_base_cpu_set_t (so we > >> allow the cpus to be potentially numbered up to > >> OPAL_PAFFINITY_BITMASK_CPU_MAX - 1). > >> > >> The problem with module_set() is that is loops over > >> OPAL_PAFFINITY_BITMASK_T_NUM_BITS bits to check if these bits are set in > >> the mask: > >> > >> for (i = 0; ((unsigned int) i) < OPAL_PAFFINITY_BITMASK_T_NUM_BITS; ++i) > >> { > >> if (OPAL_PAFFINITY_CPU_ISSET(i, mask)) { > >> hwloc_bitmap_set(set, i); > >> } > >> } > >> > >> Given "mask"'s type, I think module_set() should instead loop over > >> OPAL_PAFFINITY_BITMASK_CPU_MAX bits. > >> > >> Note that module_set() uses a type for its internal mask that is > >> coherent with OPAL_PAFFINITY_BITMASK_T_NUM_BITS (hwloc_bitmap_t). > >> > >> So I'm wondering whether this is a known limitation I've never heard of > >> or an actual bug? > >> > >> Regards, > >> Nadia > >> > >> > >> _______________________________________________ > >> devel mailing list > >> de...@open-mpi.org > >> http://www.open-mpi.org/mailman/listinfo.cgi/devel > >> ----- > >> No virus found in this message. > >> Checked by AVG - www.avg.com > >> Version: 10.0.1392 / Virus Database: 1520/3864 - Release Date: 08/28/11 > >> > >> _______________________________________________ > >> devel mailing list > >> de...@open-mpi.org > >> http://www.open-mpi.org/mailman/listinfo.cgi/devel > > > > > _______________________________________________ > devel mailing list > de...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/devel
