Many processes stuck in zfs

[Stefan Bethke]

Am 09.03.2010 um 11:53 schrieb Peter Jeremy:

> On 2010-Mar-09 10:15:53 +0100, Stefan Bethke <stb at lassitu.de> wrote:
>> Over the past couple of months, I've more or less regularly observed machines having more and more processes stuck in the zfs wchan.  The processes never recover from that,
> 
> How long have you waited?

Many hours, sometimes up to 48 hours (when I didn't notice the stuck processes at first).

> There seems to be a problem with low free memory handling that causes ZFS
> to turn into cold molasses.  The work-around is to run a program that
> allocates a decent size chunk of memory and then exits.  The original
> suggestion was something like:
> 	perl -e '@x = (0) x 1000000;'
> I've written a short program that allocates and dirties ~100MB and then
> exits and run it from cron.

I'll try that the next time I encounter the stuck processes.

I'm recording ZFS ARC stats with munin, would I be able to identify such a low memory situation from there?  Would it make sense to monitor other stats?


Thanks,
Stefan

-- 
Stefan Bethke <stb at lassitu.de>   Fon +49 151 14070811