dynamic ARC tuning
zfsonlinux has the ability to dynamically tune ARC variables. Having this capability in illumos would be very helpful to SmartOS and OmniOS to be able to get the ARC out of the way of bhyve instances, which require guest memory to be resident. See https://smartos.org/bugview/OS-8005.
Updated by Mike Gerdts 14 days ago
arc_tuning_update was added as part of the port of #5376 to zfsonlinux. That port was far from straight-forward: the diffs in illumos and zol are quite different.
NB: zol arc_shrink is illumos arc_reduce_target_size