DEVFS in a chroot?

[M. Warner Losh]

In message: <7432.1083333726 at critter.freebsd.dk>
            "Poul-Henning Kamp" <phk at phk.freebsd.dk> writes:
: In message <20040430.075448.70646001.imp at bsdimp.com>, "M. Warner Losh" writes:
: >In message: <6695.1083331489 at critter.freebsd.dk>
: >            "Poul-Henning Kamp" <phk at phk.freebsd.dk> writes:
: >: In message <20040430.070341.26991317.imp at bsdimp.com>, "M. Warner Losh" writes:
: >: >In message: <5473.1083327210 at critter.freebsd.dk>
: >: >            "Poul-Henning Kamp" <phk at 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...

How would that make it worse?  Seems like I'm in a no win situation:
if I mount one for everybody, then the system grinds to a halt because
the mount lists are too long.  If I mount and unmount it all the time,
things are also bad in some unspecified way.

Warner