There is a new whitepaper on TechDocs, that describes the HowTo setup the Linux distributions RHEL 7.2 and SLES 12 SP1, so that OpenSSH (and all workloads using this) really benefit from the hardware encryption delivered with System z.
One of their key outcomes is that you either need to specify the accelerated ciphers explicitly or put them at the top of the search order of OpenSSH.
Abstract: “This article summarizes our experiences with the configuration and usage
of OpenSSH using hardware cryptographic support of IBM z Systems. We
report our findings in the areas of performance and throughput
improvement. Our positive experience indicates that you should make use
of this capability when using OpenSSH.”