ZFS ARC tuning: vfs.zfs.arc.max

From: Graham Perrin <grahamperrin_at_gmail.com>
Date: Sun, 14 Sep 2025 01:04:56 UTC
On 14/09/2025 01:16, Rick Macklem wrote:
> On Fri, Sep 12, 2025 at 8:02 PM Graham Perrin<grahamperrin@gmail.com> wrote:
>> On 13/09/2025 03:25, Rick Macklem wrote:
>>
>>> …
>>> - setting vfs.zfs.arc_max to a much smaller value than 99.9% and …
>>
>> vfs.zfs.arc_max is recognised, but legacy.
> At least I can see this is used to set zfs_arc_max. See below..
>
>> More modern:
>>
>> vfs.zfs.arc.max
> I'm blind. I can't even figure out where/what this sets.
> (If it also sets zfs_arc_max, I cannot find where in the code it does so?
> Or does it set nothing at all?)


FreeBSD: Add legacy arc_min and arc_max · freebsd/freebsd-src@0421f25 
<https://github.com/freebsd/freebsd-src/commit/0421f257b20f41e33fb69e067b47beed2c5bd3bd>

Upstream:

FreeBSD: Add legacy compat arc_min and arc_max tunables · Pull Request 
#10579 · openzfs/zfs <https://github.com/openzfs/zfs/pull/10579>