This was a bug in ZFS itself, and was resolved years ago: https://smartos.org/bugview/OS-6404
In FreeBSD 12.x and older, you could opt out of using UMA with: vfs.zfs.zio.use_uma=0, but that is not necessary
In FreeBSD 12.x and older, you could opt out of using UMA with: vfs.zfs.zio.use_uma=0, but that is not necessary
I’m on 13-RELEASE.