It was first implemented on Illumos and then ported to ZoL. This patch is a port to FreeBSD of the ZoL version. This patch also includes a fix for a race condition that was amended With such patch Delphix has seen a huge decrease in latency of the mount phase (https://github.com/openzfs/openzfs/commit/a3f0e2b569 for details). With that current change Gandi has measured improvments that are on par with those reported by Delphix. Zol commits incorporated:a10d50f999
e63ac16d25
Reviewed by: avg, sef Approved by: avg, sef Obtained from: ZoL MFC after: 1 month Relnotes: yes Sponsored by: Gandi.net Differential Revision: https://reviews.freebsd.org/D19098