Good catch; fixed. On Apr 23, 2012, at 4:40 PM, George Bosilca wrote:
> No strong opinion. However, the comment about the initial value of > opal_cache_line_size is wrong (opal/runtime/opal.h), as it states that the > default value is -1 while it is 128. > > george. > > On Apr 23, 2012, at 16:21 , Jeffrey Squyres wrote: > >> No one replied to this RFC. Does anyone have an opinion about it? >> >> I have attached a patch (including some debugging output) showing my initial >> implementation. If no one objects by the end of this week, I'll commit to >> the trunk. >> >> Terry: please add this to the agenda tomorrow. >> >> >> On Mar 30, 2012, at 1:09 PM, Jeffrey Squyres wrote: >> >>> I was just recently reminded of a comment that is near the top of >>> opal_init_util(): >>> >>> /* JMS See note in runtime/opal.h -- this is temporary; to be >>> replaced with real hwloc information soon (in trunk/v1.5 and >>> beyond, only). This *used* to be a #define, so it's important >>> to define it very early. */ >>> opal_cache_line_size = 128; >>> >>> A few points: >>> >>> 1. On my platforms, hwloc tells me that my cache line size is 64, not 128. >>> Probably not a tragedy, but... >>> >>> 2. I see opal_cache_line_size being used in a lot of BTL and PML >>> initialization locations. I see it being used in opal/class/free_list.*, >>> too. >>> >>> 3. I poked around with this yesterday to see if we could have hwloc >>> initialize the opal_cache_line_size value. Points to remember: >>> >>> - we initialize the opal hwloc framework in opal_init(), but we do not load >>> the local machine's architecture then (because it can be expensive, >>> particularly if lots of MPI processes are all doing it simultaneously) >>> - instead, the local machine topology is discovered once by each orted >>> (using hwloc) and then RML sent to each local MPI process, where it is >>> locally loaded into each MPI proc's hwloc tree >>> - this happens during the orte_init() in ompi_mpi_init() >>> >>> Meaning: we can initialize the opal_cache_line_size in MPI processes during >>> orte_init(). >>> >>> Is this acceptable to everyone? >>> >>> If so, I can go ahead and code this up. I would probably leave the initial >>> value hard-coded to 128 (just in case something uses it before >>> orte_init()), and then later during orte_init(), reset it to the smallest >>> L1 cache size that hwloc finds on the machine. >>> >>> -- >>> Jeff Squyres >>> jsquy...@cisco.com >>> For corporate legal information go to: >>> http://www.cisco.com/web/about/doing_business/legal/cri/ >>> >>> >>> _______________________________________________ >>> devel mailing list >>> de...@open-mpi.org >>> http://www.open-mpi.org/mailman/listinfo.cgi/devel >> >> >> -- >> Jeff Squyres >> jsquy...@cisco.com >> For corporate legal information go to: >> http://www.cisco.com/web/about/doing_business/legal/cri/ >> <opal-cache-line-size.diff>_______________________________________________ >> 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 -- Jeff Squyres jsquy...@cisco.com For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/
