[nccl flight recorder] record time we discover start and complete (#119249)
Some APIs like ncclCommAbort can cause nccl kernels to finish even if
they were previously stuck. Because we can gather the trace buffer after
those calls, we can end up seeing some collectives marked completed eventhough
that complete happened several minutes after they started and clearly after
the timeout. This changes how we record state so that we keep track of the time
we discover a state change, so even if eventually the collective gets marked complete,
we can observe it happened minutes after it was schedule.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/119249
Approved by: https://github.com/wconstab
