Hyper-V Live Migration with RDMA enabled: unclear downtime threshold during final memory copy

Live Migration of a small application VM with RDMA enabled

I am planning to move a small application running in a Hyper-V VM between two hosts using Live Migration, with the goal of no perceptible downtime for users. The research available to me confirms that Live Migration is a documented zero-downtime feature, and that RDMA (SMB Direct) can be used to speed up the memory transfer phase.

What is unclear

Microsoft's documentation describes migration time as proportional to VM memory size and available network bandwidth, but I cannot find any documented threshold or guarantee for the brief pause during the final memory copy phase when RDMA is enabled. Community reports mention a few seconds of downtime in that phase, but this does not appear to be officially confirmed, so I cannot tell whether enabling RDMA actually reduces that final pause or only speeds up the bulk transfer.

Constraints

Both hosts run the same Hyper-V version with identical virtualization configuration, as required. The application is latency-sensitive enough that even a multi-second freeze during cutover would be noticeable.

1. Does enabling RDMA for Live Migration measurably shorten the final memory-copy pause, or only the overall migration duration?

2. Is there any documented or supportable downtime threshold for the cutover phase, or is it purely dependent on dirty-page rate and bandwidth?

3. What is a practical way to measure the actual cutover pause on a test pair of hosts before migrating the production VM?