is TMPFS still highly experimental?

[Artem Belevich]

> For me, the bug is still here:
> $ uname -a
> FreeBSD b 8.2-STABLE FreeBSD 8.2-STABLE #5: Wed Sep 14 15:01:25 CEST 2011
>   root at buildervm:/data/usr/obj/data/usr/src/sys/BOOTCLNT  amd64
> $ df -h /tmp
> Filesystem    Size    Used   Avail Capacity  Mounted on
> tmpfs           0B      0B      0B   100%    /tmp
>
> I have no swap configured. The machine has 64 GB RAM.
> vm.kmem_size=60G; vfs.zfs.arc_max=55G; vfs.zfs.arc_min=20G

I'm curious -- does your ARC size ever reaches configured limit of
55G? My hunch that it's probably hovering around some noticeably lower
number.

On my ZFS setups a lot of memory seems to be lost due to
fragmentation. On a system with 24G of RAM and rac_max=16G, I
typically see more than 20G of memory wired.
With kmem_size=60G, ARC is likely to use up most of available kmem
space and that's probably what affects tmpfs. Besides, with kmem_size
that close to arc_max you may be risking meeting "kmem too small"
panic, though, considering that your kmem_size is rather large chances
of that are smaller than on a system with smaller amounts of memory
and kmem_size.

I'd start with doubling kmem_size and, possibly, reducing arc_max to
the point where it stops putting pressure on tmpfs.

--Artem