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Tomislav Janjusic edited this page Jan 6, 2024 · 1 revision

December 2012 OMPI Developer's Meeting

Thursday, Dec. 6, 2012:

Friday, Dec. 7, 2012:

Note that this overlaps with the last day of the December 3-6 2012 MPI Forum meeting, mainly because we believe that the Forum will finish before Thursday. :-)

Attendance:

  • Jeff Squyres
  • Ralph Castain
  • Brian Barrett (Thu only; leaving Fri morning)
  • Brice Goglin
  • Josh Hursey
  • Nathan Hjelm
  • Sam Gutierrez
  • Rich Graham (likely only Thursday)
  • Geoffroy Vallee (CANCEL)
  • Takahiro Kawashima (only Thursday)
  • Manjunath Gorentla Venkata (Thu only)

Agenda topics (in no particular order):

  • Mellanox: OB1 bottleneck / profiling results
  • Brian: progress callbacks from requests
  • Brian: memory reduction
  • Brian: fix thread safety brokenness in PMLs
  • Brian: NBC on intercommunicators
  • Brian / Ralph: async progress
  • ORNL: ORCA patch
  • hwloc: if anybody wants to discuss where hwloc is going, Brice will be here
  • Ralph: stale code (Windows, Solaris, C/R)
  • Ralph: ORTE progress thread status, event lib thread support
  • Ralph: rewrite of RML/OOB status
  • Ralph: movement of BTLs
  • Ralph: extend BTL/MTL to include "modex reqd" flag
  • Jeff: RPATH flags in wrapper compilers (trac ticket 376)
  • Jeff: Windows support possibility (John Cary)
  • Nathan: MCA framework updates
  • MPI-2.2/MPI-3 compliance

Notes:

  • Asynch progress
    • Portals 4 progress engine tried the spin and block model; hard to get small message latency down
    • Rather than push an asynch progress for all messages model, let upper layer protocols choose
    • Non-blocking collectives currently wouldn't get async progress. Would have to change to a model where the request callbacks are used instead of registering an opal_progress function
    • What do do with ENABLE_PROGRESS_THREADS? Might be best to delete it?
      • Brian sent a note to George with the details
    • Brian is going to enable thread support by default, so that we can start testing thread corner cases
    • Nathan is going to look at FREELIST_WAIT to try to reduce the recursion, which will help with the recursion behavior which can cause trouble out of an asynch callback.
  • Memory reduction
    • Big scaling problem is the endpoint structure size in BTLs, someone needs to look at this in OpenIB
    • Other problems are the modex (can make this shared on node and more polling based) and the ompi_proc_t
    • Ralph looking at dealing with modex
    • Brian going to remove the list_item_t from ompi_proc_t and add accessor functions for everything not performance critical in ompi_proc_t so that we can make some of the pointers (like convertor) be global when homogeneous build.
  • Progress callbacks from requests
    • No one knew what this was
    • However, we had a long conversation about ROMIO and non-blocking and decided
    • Jeff will implement the MPIX functions for grequest.
  • Non-blocking collectives / communicator creation
    • Discussion about how to implement the non-blocking communicator creation. We ran into some fairly serious problems in design, because we allow communication during collective creation
    • Jeff is going to update this piece later.
  • long discussion about MPIT
    • Nathan will keep working on this
  • long discussion about ORCA
  • Remove this as a layer, and move to a framework in OMPI
  • static framework a la libevent
  • Geoffray is going to work on this in his bitbucket
  • linking
  • Jeff will make the wrapper compilers recognize static
  • Brian will do --with-orte, .... (i have this in a picture)
  • moving the BTL's down to OPAL
    • Issues:
      1. naming (ompi_proc_t)
      2. initialization
      3. endpoint sharing
      4. tag allocation
        • opal header file. Put in a comment saying that if anyone wants one, buy an OMPI developer a beer and we'll commit it for you
      5. what comes down?
        • BTL, mpool, rcache, allocator, some common
        • move BML -> BTL base
    • Ralph to fill in more details on the decided design.
    • Ralph will setup a bitbucket for this work.
    • GP people will start working on this in Jan/Feb.
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