Date: Fri, 30 Apr 2004 08:52:04 -0700 From: Wes Peters <wes@softweyr.com> To: freebsd-current@freebsd.org Cc: "M. Warner Losh" <imp@bsdimp.com> Subject: Re: DEVFS in a chroot? Message-ID: <200404300852.04723.wes@softweyr.com> In-Reply-To: <7432.1083333726@critter.freebsd.dk> References: <7432.1083333726@critter.freebsd.dk>
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On Friday 30 April 2004 07:02, Poul-Henning Kamp wrote:
> In message <20040430.075448.70646001.imp@bsdimp.com>, "M. Warner Losh"
writes:
> >In message: <6695.1083331489@critter.freebsd.dk>
> >
> > "Poul-Henning Kamp" <phk@phk.freebsd.dk> writes:
> >: In message <20040430.070341.26991317.imp@bsdimp.com>, "M. Warner Losh"
writes:
> >: >In message: <5473.1083327210@critter.freebsd.dk>
> >: >
> >: > "Poul-Henning Kamp" <phk@phk.freebsd.dk> writes:
> >: >: >Should I mount /var/chroot/dev as type devfs?
> >: >:
> >: >: Yes:
> >: >:
> >: >: mount -t devfs randomargument /var/chroot/dev
> >: >
> >: >What if I have hundreds of these chroots? We build our product
> >: > inside a chroot right now and I'm worried what the overhead of
> >: >mounting/unmounting this for every build would be...
> >:
> >: As far as I recall, our mountlist handling is not optimised for
> >: hundreds of simultaneous mountpoints: we basically walk the list.
> >: That said, I belive we only do so during the actual mount/unmount
> >: operations, so I do not think there is a performance issue as such.
> >
> >Would the performance issues be mitigated by mounting/unmounting devfs
> >all the time? Eg, only mount it while it is actively being used?
>
> I think you would actually make it worse that way...
We do this on our build box -- mount and unmount both devfs and a read-only
source directory, chroot, and build, as in:
/usr/wes/products on /usr/obj/buildenvs/usr/wes/products/iamsrc (nullfs,
local, read-only)
devfs on /usr/obj/buildenvs/usr/wes/products/dev (devfs, local)
And then unmount once the build has completed. We have 'chroot' and
'unmount' targets in the top-level makefile to get back into and out of the
chroot as well.
On 5.2.1, our build box hangs once or twice a week on an unmount. I'm not
sure if it's the nullfs or the devfs unmount. I haven't had time to debug
this, I've been ankle deep (head first) in PHP and Perl code that are the
guts of my product for 6 weeks now, but I'll try to catch it in the
debugger next week once the smoke clears.
I run -CURRENT on my workstation and it has not hung in a while, but it
doesn't get pounded the way the buildbox does. Is there some resource
related to mounts that might be getting leaked?
--
Where am I, and what am I doing in this handbasket?
Wes Peters wes@softweyr.com
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