Swap on ZFS Volume still panics?

[App Deb]

Yes sorry for actually calling it a panic, it is a deadlock, I didn't see
any messages, anyway the system becomes unusable and needs a manual hard
reboot.

I found the mention (without any warnings) here:
http://wiki.freebsd.org/RootOnZFS

I have tried this on 3 different systems (all 8.1R though) and they always
deadlock once the zfs swap is touched.

I think that the "not recommended" is not enough. It just doesn't work at
all, except if I am doing something wrong and there are some cases that it
works?

I have now switched to native freebsd-swap (after a long zfs send/receive
backup to resize the zpool :) ) and everything works great.

Thanks.

On Fri, Sep 10, 2010 at 10:39 AM, Pawel Jakub Dawidek <pjd at freebsd.org>wrote:

> On Wed, Sep 08, 2010 at 07:19:40PM +0300, App Deb wrote:
> > Reading the wiki guides they mention the official way to add swap volumes
> on
> > ZFS (set org.freebsd:swap=on etc..),
> >
> > So I thought that it should work now, But I just got a panic in
> 8.1-RELEASE
> > after a heavy memory situation that touched swap for the first time.
>
> Swap on ZVOL is still not recommended. Where did you find information
> that it now recommended? I can't find anything about swap on
> http://wiki.freebsd.org/ZFS and on
> http://wiki.freebsd.org/ZFSQuickStartGuide there is a note that it is
> not recommended. Let me know where it is advised and I'll remove it or
> add a note (if the documentation is mine).
>
> > It is a hassle to add gmirror volumes for swap on full zfs systems, is
> there
> > any workaround for this, or any news when a fix is coming or if it is
> > coming?
>
> I've no plans to fix it, maybe with ZFSv28 it will be easier to fix, but
> this is really low priority. If you use full ZFS system the recommended
> layout is described here:
>
>
> http://blogs.freebsdish.org/pjd/2010/08/06/from-sysinstall-to-zfs-only-configuration/
>
> > If the current code procudes guaranteed panics with zfs swap, I think
> that
> > every mention of swap on zfs should be removed from the semi-official
> wiki
> > guides.
>
> BTW. If this issue will be worked on in the future, it will be useful to
> actually see your panic, backtrace and other debug info. To be honest, I
> didn't expect it to panic, rather deadlock. Maybe panic is from deadlock
> resolver? Hard to say without any debug info.
>
> --
> Pawel Jakub Dawidek                       http://www.wheelsystems.com
> pjd at FreeBSD.org                           http://www.FreeBSD.org
> FreeBSD committer                         Am I Evil? Yes, I Am!
>