ZFS on rpi3

[Sad Clouds <cryintothebluesky%gmail.com@localhost>]

I'm trying out NetBSD-9 with ZFS on raspberry pi 3. I have 128GB USB SD
card which has ZFS setup. Noticed that sometimes when under heavy use
something goes wrong and pgdaemon spins on CPU 100% all the time.

Not sure if this is something to do with small amount of RAM on this
machine. Are there any tunables like in FreeBSD

vm.kmem_size="330M"
vm.kmem_size_max="330M"
vfs.zfs.arc_max="40M"
vfs.zfs.vdev.cache.size="5M"

that make ZFS play nice when low on RAM? Looked at "sysctl -a" but
there are only kstat parameters, I assume they are only for statistics
and don't affect run-time?