Compare the old protocol (clients send no maxAwaitTimeMS nor topologyVersion and don't set exhaustAllowed) with the new protocol (awaitable isMaster plus exhaust). We already have a workload that tests the performance of primary required reads in the face of stepdowns. Verify that a higher percentage of reads succeed with the new protocol, and verify that total throughput is higher. The test does not directly report the client time to recovery, but according to David Daly, "The underlying tool reports individual operation latencies, so we can figure out the exact recovery time after stepdown, although that may require some extra post-processing." Do this if we judge it worth the effort.