Recent qemu and timers issue

[Juergen Lock]

In article <200904062254.37824.kalinoj1 at iem.pw.edu.pl> you write:
>Dnia sobota 04 kwietnia 2009 o 00:23:29 Juergen Lock napisa=C5=82(a):
>> In article <c948bb4de85d1b2a340ac63a7c46f6d9 at iem.pw.edu.pl> you write:
>> >Hi all,
>> >
>> >When running FreeBSD 8-CURRENT system inside a qemu machine (from the
>> >latest port by nox at freebsd.org) I have strange timer problems in the
>> >virtual machine.
>>
>> What is the host running, also current?
>
>Yes, the host is also running current.=20
>
>But the same host has no problem with older FreeBSD kernels on the guest, e=
>g.=20
>=46reeSBIe 1.1 or FreeNAS (kernel  v.6.4)
>
OK I did some tests in the meantime on my newest box that has 4 cpus and
is running 7-stable: (host)
>>
>> >My logs and console are full of messages like this:
>> >calcru: runtime went backwards from 11248014678717988 usec to 119242 usec
>> >for pid 60 (ps)
>> >
>> >calcru: runtime went backwards from 11248014678921829 usec to 2516605 us=
>ec
>> >for pid 60 (ps)
>> >calcru: runtime went backwards from 7014844 usec to 6270851 usec for pid=
> 0
>> >(kernel)
>> >
>> >It even happens for some processes to die inside qemu guest.
>>
>>  Is this an smp host?  You could try forcing qemu onto one cpu by
>> doing like:
>> 	cpuset -l 0 qemu ...
>>
>
>Yes, it's an smp host (8 cpus). But cpuset -l 0 qemu ... (also -clock=20
>dynticks) didnt't help.
>
 Same here with an 8.0-HEAD-20090403-JPSNAP-i386 guest.  (OK I didn't see
guest processes die, but I also didn't really load the guests so far...)

 A 7.1-RELENG_7-20090403-JPSNAP-i386 guest was not affected.

>> >I tried to use all possible timers using sysctl, where I have:
>> >TSC(800) HPET(900) ACPI-safe(850) i8254(0) dummy(-1000000)
>> >None of these helped.
>>
>>  On the host or in the guest?
>>
>
>It's in the guest machine., where I tried these settings=20
>
>One important thing I forgot to mention in my initial posting:
>When I run 'systat -vm 1' o the guest machine - it's almost fully loaded - =
>and=20
>80% (or more) of it's cpu time is spent in interrrupt handling! This is als=
>o=20
>not the case with older kernels.
>
 Hmm 'systat -vm 1' doesn't really load the 8.0 guest here.

>> [snip]
>> >I would greatly appreciate any help or a hint - where should I look for
>> >help on this issue.
>>
>>  If none of these help you could also try the qemu list:
>> 	http://lists.nongnu.org/mailman/listinfo/qemu-devel
>> (I think you can still post without being subscribed, altho in that case
>> it may take a while for the post to get thru.)
>>
>>  HTH,
>> 	Juergen
>
>At this moment it's very hard for me to judge if it's qemu or kernel issue..
>Any thoughts?

 Yeah, could be one or the other.

 Also kinda out of ideas...
	Juergen