zfs kernel panic

Pawel Jakub Dawidek pjd at FreeBSD.org
Wed Sep 9 10:44:02 UTC 2009

On Wed, Sep 09, 2009 at 07:41:08PM +1000, Danny Carroll wrote:
> On 9/09/2009 6:33 PM, Pawel Jakub Dawidek wrote:
> >On Wed, Sep 09, 2009 at 09:07:15AM +0200, Gerrit Kühn wrote:
> >   
> >>On Tue, 8 Sep 2009 18:44:13 +0200 Pawel Jakub Dawidek<pjd at FreeBSD.org>
> >>wrote about Re: zfs kernel panic:
> >>
> >>PJD>  If this is amd64, add vm.kmem_size="4G" to your loader.conf back.
> >>
> >>What about vm.kmem_size_max? Does that also need tuning?
> >>     
> >No, this should be auto-tuned to some very large value.
> >
> >   
> Pawel (et al),
> Would it be possible for you to post to the list your ideas of a 
> complete set of tuning parameters for ZFS on amd64?  I have used the 
> wiki article as a reference (http://wiki.freebsd.org/ZFSTuningGuide) but 
> it states that if you have > 2g ram and 7.2 then you do not need to tune 
> at all.

I think that was the idea, although I see no reason to have less kernel
address space than physical memory (except there might be other
in-kernel variables auto-tuned based on kmem size).

> I for one would be interested in learning a little more about how the 
> memory should be tuned.  Specifically what might be interesting is to 
> know, once a parameter is set, is there an easy way to find out how it's 
> being used? i.e. If you start limiting the arc, is is possible to know 
> what sort of hit/miss rate you are getting.

There are ARC statistics available here:

	# sysctl kstat.zfs

Pawel Jakub Dawidek                       http://www.wheel.pl
pjd at FreeBSD.org                           http://www.FreeBSD.org
FreeBSD committer                         Am I Evil? Yes, I Am!
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