On Tue, Mar 03, 2026 at 02:25:11PM -0800, Rick Macklem wrote:
| On Tue, Mar 3, 2026 at 12:33 PM Doug Ambrisko <[email protected]> wrote:
| >
| > On Sun, Nov 02, 2025 at 11:48:06AM +0100, Alexander Leidinger wrote:
| > | Am 2025-10-29 22:06, schrieb Doug Ambrisko:
| > | > It seems around the switch to OpenZFS I would have arc clean task
| > | > running
| > | > 100% on a core. I use nullfs on my laptop to map my shared ZFS /data
| > | > partiton into a few vnet instances. Over night or so I would get into
| > | > this issue. I found that I had a bunch of vnodes being held by other
| > | > layers. My solution was to reduce kern.maxvnodes and vfs.zfs.arc.max so
| > | > the ARC cache stayed reasonable without killing other applications.
| > | >
| > | > That is why a while back I added the vnode count to mount -v so that
| > | > I could see the usage of vnodes for each mount point. I made a script
| > | > to report on things:
| > |
| > | Do you see this also with the nullfs mount option "nocache"?
| >
| > I seems to have run into this issue with nocache
| > /data/jail/current/usr/local/etc/cups
/data/jail/current-other/usr/local/etc/cups nullfs rw,nocache 0 0
| > /data/jail/current/usr/local/etc/sane.d
/data/jail/current-other/usr/local/etc/sane.d nullfs rw,nocache 0 0
| > /data/jail/current/usr/local/www
/data/jail/current-other/usr/local/www nullfs rw,nocache 0 0
| > /data/jail/current/usr/local/etc/nginx
/data/jail/current-other/usr/local/etc/nginx nullfs rw,nocache 0 0
| > /data/jail/current/tftpboot /data/jail/current-other/tftpboot
nullfs rw,nocache 0 0
| > /data/jail/current/usr/local/lib/grub
/data/jail/current-other/usr/local/lib/grub nullfs rw,nocache 0 0
| > /data/jail
/data/jail/current-other/data/jail nullfs rw,nocache 0 0
| > /data/jail /data/jail/current/data/jail
nullfs rw,nocache 0 0
| >
| > After a while (a couple of months or more). My laptop was running slow
| > with a high load. The perodic find was running slow. arc_prunee was
| > spinning. When I reduced the number of vnodes then things got better.
| > My vfs.zfs.arc_max is 1073741824 so that I have memory for other things.
| >
| > nocache does help taking longer to get into this situation.
| Have any of you guys tried increasing vfs.zfs.arc.free_target?
|
| If I understand the code correctly, when freemem < vfs.zfs.arc.free_target
| the reaper thread (the one that does uma_zone_reclaim() to return pages
| to the system from the uma keg that the arc uses) should be activated.
I haven't tried that. I set:
kern.maxvnodes
vfs.zfs.arc.min
vfs.zfs.arc.max
vfs.zfs.prefetch.disable=1
I need to make sure kern.maxvnodes is small enough so it doesn't thrash
when vfs.zfs.arc.max set to 1G. The issues tend to take a while to
happen. On the plus side I can adjust these when I hit them mostly by
reducing kern.maxvnodes without having to do a reboot.
Thanks,
Doug A.
