[Bug 265424] vfs.zfs.arc_min ignored in /boot/loader.conf but works in /etc/sysctl.conf

From: <bugzilla-noreply_at_freebsd.org>
Date: Sun, 24 Jul 2022 19:48:27 UTC
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=265424

            Bug ID: 265424
           Summary: vfs.zfs.arc_min ignored in /boot/loader.conf but works
                    in /etc/sysctl.conf
           Product: Base System
           Version: 13.1-STABLE
          Hardware: Any
                OS: Any
            Status: New
          Severity: Affects Only Me
          Priority: ---
         Component: kern
          Assignee: bugs@FreeBSD.org
          Reporter: jon@xyinn.org

Hello,

I'm currently running (but most likely also affects 13.1-RELEASE):

FreeBSD 13.1-STABLE #0 stable/13-n251909-fa872a4bf71: Sun Jul 24 10:33:02 EDT
2022     root@leslie:/usr/obj/usr/src/amd64.amd64/sys/GENERIC amd64

From my experiments, it seems that `vfs.zfs.arc_min` is ignored in
/boot/loader.conf but it works in /etc/sysctl.conf. I'm not sure if it's
related to a race condition or just the linear sequence of execution not
considering the arc min (maybe too early?). Using quotes or not made no
difference. The interesting this is that `vfs.arc.arc_max` works fine in
/boot/loader.conf, and in /etc/sysctl.conf (as stated in 20.6.1 of the
documentation for both tunables).

These are my settings:

# ZFS Tuning
vfs.zfs.arc_min="4294967296"
vfs.zfs.arc_max="8589934592"
vfs.zfs.prefetch.disable="1"

If you place those in /boot/loader.conf, only `arc_max` and `prefetch.disable`
will be set properly, `arc_min` will be 0. If I place the same exact stuff in
/etc/sysctl.conf, all of them will be set properly.

- Jonathan

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