Heads-up: Possible regression between 10.0-RELEASE and 10.1-BETA1 with '/ on ZFS' setup

[Steven Hartland]

----- Original Message ----- 
From: "Glen Barber" <gjb at FreeBSD.org>
> On Sat, Oct 04, 2014 at 04:03:39PM +0100, Steven Hartland wrote:
> > >>On Sat, Oct 04, 2014 at 03:51:39AM +0100, Steven Hartland wrote:
> > >>> > This has been a known issue on i386 since the switch to Clang see UPDATING:
> > >>> 20121223:
> > >>>        After switching to Clang as the default compiler some users of ZFS
> > >>>        on i386 systems started to experience stack overflow kernel panics.
> > >>>        Please consider using 'options KSTACK_PAGES=4' in such configurations.
> > >>> > In my experience your millage may vary but essentially without 4 stack pages
> > >>> > all bets are off in terms of stability.
> > 
> > Oh and just looking at the code kern.kstack_pages is read only so wont have
> > any effect, hence you will definitely need to set the kernel option as per
> > the UPDATING entry.
> > 
> 
> Indeed, it is readonly.  I'm building kernel on the test VM, but may
> have to get the kernel built somewhere else from a non-ZFS VM, because
> the i386 VM with ZFS is unusable.
> 
> I'm not familiar with these parts of the kernel internals.  What is the
> harm in making KSTACK_PAGES=4 the default in i386 GENERIC ?
> 

I expect on the smaller hardware we'd be eating into precious memory, but
its a good question.

You can always detach the second disk while you build and then re-attach it
after you have the new kernel installed if that helps?

    Regards
    Steve