Re: [Xen-users] ntpd under Xen Dom0 exhibits extremely high jitter/noise? runs stable/quiet under non-xen kernel.

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Wed, Jan 13, 2010 at 10:38:18PM +0200, Pasi Kärkkäinen wrote:
> On Wed, Jan 13, 2010 at 08:39:40PM +0200, Pasi Kärkkäinen wrote:
> > On Wed, Jan 13, 2010 at 10:25:45AM -0800, mail ignored wrote:
> > > On Wed, Jan 13, 2010 at 10:12 AM, Pasi Kärkkäinen <pasik@xxxxxx> wrote:
> > > > OK.. so you might want to report a bug to the opensuse bugzilla.
> > > 
> > > so it *is* a bug.  ok, i'll file @ opensuse. thanks.
> > > 
> > 
> > I think it's actually two different bugs :)
> > 
> > 1) You should be able to limit the number of dom0 vcpus by dom0_vcpus option
> > 2) It shouldn't crash when you remove vcpus from dom0 using vcpu-set.
> > 
> > > > "dom0_vcpus=1 dom0_vcpus=pin" options should do it.
> > > > Verify with "xm dmesg" that there parameters are really there.
> > > 
> > > seem to be,
> > > 
> > > xm dmesg | egrep -i "dom0|vcp"
> > >  (XEN) Command line: loglvl=all loglvl_guest=all dom0_mem=1024M
> > > vga=gfx-1280x1024x32 console=vga,com1 com1=57600,8n1 iommu=1
> > > cpufreq=xen:performance cpuidle dom0_vcpus=1 dom0_vcpus_pin
> > > sched=credit
> > >  (XEN)  Dom0 kernel: 64-bit, lsb, paddr 0x2000 -> 0x8e1000
> > >  (XEN)  Dom0 alloc.:   0000000216000000->0000000218000000 (253952
> > > pages to be allocated)
> > >  (XEN) Dom0 has maximum 4 VCPUs
> > >  (XEN) *** Serial input -> DOM0 (type 'CTRL-a' three times to switch
> > > input to Xen)
> > > 
> > > but it is, then.
> > >
> > 
> > I'll test dom0_vcpus option on my testbox at some point, with Xen 3.4.x.
> > I've been using it successfully with Xen 3.1.x, on RHEL5/CentOS5.
> > 
> 
> I just tried it on my Fedora 12 testbox with Xen 3.4.2, and I'm seeing
> the same behaviour:
> 
> (XEN) Xen version 3.4.2 (root@(none)) (gcc version 4.4.2 20091027 (RedHat 
> 4.4.2-7) (GCC) ) Mon Dec 14 06:53:18 EET 2009
> (XEN) Latest ChangeSet: unavailable
> (XEN) Command line: dom0_mem=1G loglvl=all guest_loglvl=all com1=38400,8n1 
> console=com1 dom0_vcpus=1
> ..
> (XEN) Dom0 has maximum 4 VCPUs
> ..
> 
> I just sent an email to xen-devel asking about it..
> 

like Andy pointed out on xen-devel, the xen.gz option is called
dom0_max_vcpus nowadays.

I verified dom0_max_vcpus=1 works OK with Xen 3.4.2.

-- Pasi


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