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
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