Date: Sat, 4 Oct 2014 16:45:00 +0100 From: "Steven Hartland" <smh@freebsd.org> To: "Glen Barber" <gjb@FreeBSD.org> Cc: FreeBSD Release Engineering Team <re@FreeBSD.org>, freebsd-stable@FreeBSD.org Subject: Re: Heads-up: Possible regression between 10.0-RELEASE and 10.1-BETA1 with '/ on ZFS' setup Message-ID: <5AB03244BE0C425AA475302F13F3A743@multiplay.co.uk> References: <20141004024011.GC1199@hub.FreeBSD.org> <64F0D761D09546C7B47DFAA1551500BE@multiplay.co.uk> <20141004031614.GD1199@hub.FreeBSD.org> <6618E7E0B17D41D09DB9B0160C2D4DF1@multiplay.co.uk> <9E274FD2D44943ED9F9C6057068C8CE0@multiplay.co.uk> <20141004151651.GG1199@hub.FreeBSD.org>
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----- Original Message -----
From: "Glen Barber" <gjb@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
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