RBD persistent writeback cache performance

Hi, With Pacific (16.2.0) out of the door we have the RBD persistent WriteBack cache for RBD: https://docs.ceph.com/en/latest/rbd/rbd-persistent-write-back-cache/ Has anybody performed some benchmarks with the RBD cache? Interested in the QD=1 bs=4k performance mainly. I don't have any proper hardware available to run benchmarks on yet. Wido