Re: timer is off in HVM FreeBSD

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

On Sun, Nov 30, 2008 at 02:19:23AM +0900, fukumoto%imasy.or.jp@localhost wrote:
> Manuel Bouyer <bouyer%antioche.eu.org@localhost> wrote:
> >> 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
> 
> 
> I don't know how it works, isn't it emulated by QEMU?  Shouldn't it be
> sys/arch/x86/isa/clock.c (and on FreeBSD src/sys/i386/clock.c)?

It depend if it's a native kernel in a HVM guest, or a PV kernel.

> 
> Meanwhile I tried sysctl -w kern.timecounter.hardware=i8254 (or TSC)
> in FreeBSD to see if anything changes from the default ACPI-safe, but
> no difference as far as I can see.  Booting up FreeBSD in verbose mode
> I see these messages:
> 
> Calibrating clock(s) ... i8254 clock: 513169 Hz
> 513169 Hz differs from default of 1193182 Hz by more than 1%
> Timecounter "i8254" frequency 1193182 Hz quality 0
> Calibrating TSC clock ... TSC clock: 2204623115 Hz

So it looks like you have a HVM domU. What version of Xen is it ?

-- 
Manuel Bouyer <bouyer%antioche.eu.org@localhost>
     NetBSD: 26 ans d'experience feront toujours la difference
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