Re: ZFS kmem_map too small.

From: Pawel Jakub Dawidek <pjd_at_FreeBSD.org>
Date: Fri, 5 Oct 2007 20:01:19 +0200
On Fri, Oct 05, 2007 at 02:48:07AM -0700, Darren Reed wrote:
> Pawel Jakub Dawidek wrote:
> > Hi.
> > 
> > We'are about to branch RELENG_7 and I'd like to start discussion with
> > folks that experience 'kmem_map too small' panic with the latest HEAD.
> > 
> > I'm trying hard to reproduce it and I can't, so I need to gather more
> > info how you are able to provoke this panic.
> 
> Hmm, the first and only time it happened to me was when running cvsup
> on the rsync'd freebsd CVS tree after creating a snapshot of it.  I've
> repeated that exercise since (and many times before) with no problems.
> 
> That was when I mistakingly had the ARC max set to be maybe 10MB or
> so smaller than the kmem_map size (this was a mistake.)  I've since
> grown that gap to 100MB.
> 
> Tips on how to reproduce it?  Make the kmem_map size small and set the
> ARC's maximum size to be the same as it ? :)

I'm not really interested in fixing configuration bugs, although we
should do as much as we can to not allow bugus tunnings.

I'm most interested in 'kmem_map too small' panic with default
configuration, ie. no other changes than vm.kmem_size/vm.kmem_size_max.

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

Received on Fri Oct 05 2007 - 16:01:43 UTC

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