github-actions[bot]
commented
3 months ago Hello! The Git Commit Checker CI bot found a few problems with this PR:
637b40ea: UCX: Propagate MPI serialized for all worker creat...
- check_cherry_pick: does not include a cherry pick message (did you need to bot:notacherrypick?)
df838c79: pml/ucx: Propagate MPI serialized thread mode
- check_cherry_pick: does not include a cherry pick message (did you need to bot:notacherrypick?)
Please fix these problems and, if necessary, force-push new commits back up to the PR branch. Thanks!
tvegas1
replaces first v5.0.x backport #12579
cherry-pick from main #12577 and #12590
What
The UCX PML needs to differentiate between mpi serialized and single thread mode according to MPI standard.
Why
Using UCX with multiple threads, even when providing mutual exclusion, is not completely equivalent to only using UCX with one same thread.
To guarantee ordering and avoid corruption, some UCX transports need the cpu to flush stores to the devices, before another thread can progress the worker. For latency reasons, this needed flush is only performed in non single thread mode.