Dear All,
Here is a summary of today’s meeting using Zoom hub from the transcript.
A number after each sentence can refer the part of the transcript, and it is very helpful.
Regards,
Shinji.
RMA WG 2026-06-05 00:00(GMT+9:00)
Key Outcomes
The working group resolved critical threading and concurrency semantics for MPI device-side operations. Single-thread operation model adopted: each MPI operation must be issued by a single thread,
though multiple threads can issue different operations concurrently 12. Host-device epoch separation enforced: concurrent operations from host and device within the same epoch are now explicitly
erroneous, with flash operations also prohibited during concurrent device communication 34.
Decisions Made
* Threading model: Only a single thread per working group is responsible for issuing each MPI operation; multiple threads may call MPI primitives concurrently to start multiple independent operations 12
* No cooperative primitives: Decided against introducing cooperative versions (like SHMEM/NCCL-style cooperative puts) in current proposal; may revisit as future extension 15
* Thread safety alignment: Device operations always operate in MPI_THREAD_MULTIPLE mode without host-side thread model restrictions 67
* Epoch isolation: It is erroneous to call communication procedures on the same window from both host and device within the same access epoch 38
* Flash semantics: Device-side flush only flushes device-initiated operations; host-side flush must flush both host and device operations using reference counters or completion queue polling 910
* Concurrent flush prohibition: Issuing flush operations on the host concurrent with communication operations on the device is erroneous 4
Technical Clarifications
* Memory fence semantics: WinSync should be defined as a memory fence (system fence) on the device, similar to host-side shared memory behavior 1112
* Implementation flexibility: Multiple concurrent puts from different threads may be inefficient depending on implementation (e.g., proxy through host vs. direct memcopy vs. NIC access) 1314
* Race conditions: Same race condition risks exist as on CPU when multiple threads call operations without proper synchronization 1516
* Implementation overhead: Host flush of device operations requires maintaining reference counters in global memory or polling device completion queues 910
Removed Content
* "When configured correctly" sentence: Removed as non-transparent and repetitive 17
* Thread restriction paragraph: Removed confusing paragraph about MPI thread model restrictions since device operations don't share synchronization with host 67
* "As if by CPU thread" clause: Removed since windows are now separate and don't share synchronization primitives between host and device 618
Text Revisions
* Communication operations bullet expanded to clarify multiple threads can call concurrently to start multiple independent operations 19
* Erroneous condition reworded: "It is erroneous to call communication procedures on the same window from both host and device within the same epoch" 3
* Added separate sentence: "It is erroneous to issue flush operations on the host concurrent with communication operations on a device" 4
Pending Confirmation
* Implementation feasibility validation needed for host flush of device operations (reference counter overhead acceptable) 910
* Verification that no epoch manipulation primitives (lock/unlock) are exposed for GPU windows, only flush available 20
Other Updates
* Notify proposal status: First reading at forum went well with only minor changes needed; no significant opposition; proceeding to no-no vote 21
* Transcript availability: Joseph will record to cloud for automatic transcription going forward 22
Action Items
* Joseph: Review and implement minor changes from Notify proposal forum reading before next meeting 21
* Alex: Update proposal text with agreed threading model clarifications and remove identified confusing paragraphs 219
* Alex: Add concurrent flush prohibition language to proposal 4
Next Meeting
Two weeks from current meeting date 4
On 2026/06/04 木曜日 20:52, Joseph Schuchart via mpiwg-rma wrote:
> Dear all, We’ll meet again this week Thursday to continue the discussion on device-side RMA and recap the Notified RMA reading at the Forum meeting this week. As always, we’re meeting at 10am US
> Central and the connection info is available at
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> Dear all,
>
> We’ll meet again this week Thursday to continue the discussion on
> device-side RMA and recap the Notified RMA reading at the Forum meeting
> this week.
>
> As always, we’re meeting at 10am US Central and the connection info is
> available athttps://urldefense.us/v3/__https://github.com/mpiwg-rma/mpi-standard/wiki….
>
> Cheers
> Joseph
>
> ​
>
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