zfs i/o hangs on 9-PRERELEASE

[Freddie Cash]

On Fri, Nov 25, 2011 at 11:20 AM, Mark Felder <feld at feld.me> wrote:

> 13:14:32 nas:~ > uname -a
> FreeBSD nas.feld.me 9.0-PRERELEASE FreeBSD 9.0-PRERELEASE #3 r227971M:
> Fri Nov 25 10:07:48 CST 2011     root at nas.feld.me:/usr/obj/**tank/svn/sys/GENERIC
>  amd64
>
> This seemed to start happening sometime after RC1. I tried 8-STABLE and
> it's happening there too right now. I think whatever caused this was MFC'd.
> I've also reproduced this on completely different hardware running a single
> disk ZFS pool.
>
> I'm getting this output in dmesg after these hangs I keep seeing.
>
> uma_zalloc_arg: zone "pfrktable" with the following non-sleepable locks
> held:
>

There's a lot of uma_* stuff in there.  Just curious, what's the following
sysctl set to:

vfs.zfs.zio.use_uma

Back in the 8.x days, it was recommended to set it to 0 due to bugs:
http://lists.freebsd.org/pipermail/freebsd-stable/2010-June/057162.html

No idea if this is still the case or not, but you may want to try toggling
that sysctl and see if it makes a difference.

-- 
Freddie Cash
fjwcash at gmail.com