Re: timer is off in HVM FreeBSD

[Manuel Bouyer <bouyer%antioche.eu.org@localhost>]

On Fri, Nov 28, 2008 at 01:37:00AM +0900, fukumoto%imasy.or.jp@localhost wrote:
> I installed a FreeBSD 7.0/i386 as a HVM guest of NetBSD 5.99.01/amd64
> dom0, Xen 3.3 from pkgsrc.  It looks mostly working except the timer
> is off.  It is about 1.8 times slower than it should be.
> 
> # time sleep 10
> 0.000u 0.002s 0:17.99 0.0%      0+0k 0+0io 0pf+0w
> 
> Any clues?

Not much, exept it's probably not a netbsd-related issue. The timers
are managed directly by the hypervisor, not by dom0.
Here it looks like the FreeBSD kernel has a wrong idea of what the
Xen tick interrupt rate is. It's not easy to get right, because it
may be called more often than it should, or less often depending on
the load of the system. NetBSD's sys/arch/xen/xen/clock.c (including
the CVS log because it took several tries to get it right) has good
hints about how it works

-- 
Manuel Bouyer, LIP6, Universite Paris VI.           
Manuel.Bouyer%lip6.fr@localhost
     NetBSD: 26 ans d'experience feront toujours la difference
--