[Xen-users] Re: [Xen-devel] dom0-cpus problem

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Thu, Jul 23, 2009 at 10:39:27AM +0100, George Dunlap wrote:
> I didn't see the original question; but the "problem" seems to be that
> when using xend, xm vcpu-list still shows 8 vcpus for dom0?
> 
> The number of cpus for a domain is assigned at creation; in domain 0's
> case, this is at boot, necessarily before xend runs.
> 
> I suspect what (dom0-cpus 1) does is tell xend to unplug all cpus
> except one, by writing "0" into /sys/.../cpus/[1-7]/online.  This will
> tell dom0 to take vcpus 1-7 offline, which will put them in a "paused"
> state (as you can see from xm vcpu-list); but they're still registered
> to dom0 in Xen, and still available to be brought online at any time.
> 
> Setting the boot parameter will change the number of vcpus assigned on
> VM creation.
> 

Yep, thanks for explaining that.

Although the original problem was when you specify (dom0-cpus 1) you cannot
stop HVM domains anymore - they just get stuck and stay in 's' state.

I believe it's because the user is running ubuntu 2.6.24 kernel in dom0,
which most probably has this bug:

http://lists.xensource.com/archives/html/xen-devel/2009-01/msg00004.html

"Domains don't die, they just stay in the 's' state until you 'xm destroy' them"

And a fix/patch to dom0 kernel here:
http://lists.xensource.com/archives/html/xen-devel/2009-01/msg00050.html

-- Pasi

>  -George
> 
> On Wed, Jul 22, 2009 at 4:18 PM, Nerijus Narmontas<n.narmontas@xxxxxxxxx> 
> wrote:
> > On Tue, Jul 21, 2009 at 2:01 PM, Pasi Kärkkäinen <pasik@xxxxxx> wrote:
> >>
> >> On Tue, Jul 21, 2009 at 01:53:25PM +0300, Nerijus Narmontas wrote:
> >> > Hello,
> >> > If I set (dom0-cpus 1) in /etc/xen/xend-config.sxp, after I gracefully
> >> > shutdown domU, the domain stays in ---s- state.
> >> >
> >> > Is this fixed in 3.4.1-rc8?
> >> >
> >>
> >> Hello.
> >>
> >> Please don't hijack threads - you replied to a thread about network
> >> problems
> >> and gplpv drivers. Always start a new thread for new subjects.
> >>
> >> What version are you seeing this behaviour with? Xen 3.4.0 ? What dom0
> >> kernel version?
> >>
> >> -- Pasi
> >
> > Sorry for the threads thing.
> > root@xen1:/# more /etc/xen/xend-config.sxp | grep cpu
> > # In SMP system, dom0 will use dom0-cpus # of CPUS
> > # If dom0-cpus = 0, dom0 will take all cpus available
> > (dom0-cpus 1)
> > root@xen1:/# xm dmesg | grep Command
> > (XEN) Command line: console=com2 com2=115200,8n1
> > root@xen1:/# xm dmesg | grep VCPUs
> > (XEN) Dom0 has maximum 8 VCPUs
> > root@xen1:/# xm vcpu-list
> > Name                                ID  VCPU   CPU State   Time(s) CPU
> > Affinity
> > Domain-0                             0     0     5   r--       9.2 any cpu
> > Domain-0                             0     1     -   --p       1.8 any cpu
> > Domain-0                             0     2     -   --p       1.7 any cpu
> > Domain-0                             0     3     -   --p       1.6 any cpu
> > Domain-0                             0     4     -   --p       1.4 any cpu
> > Domain-0                             0     5     -   --p       1.4 any cpu
> > Domain-0                             0     6     -   --p       1.5 any cpu
> > Domain-0                             0     7     -   --p       1.3 any cpu
> > root@xen1:/# xm create /etc/xen/dc3.conf
> > Using config file "/etc/xen/dc3.conf".
> > Started domain dc3 (id=1)
> > root@xen1:/# xm vcpu-list
> > Name                                ID  VCPU   CPU State   Time(s) CPU
> > Affinity
> > Domain-0                             0     0     7   r--      36.5 any cpu
> > Domain-0                             0     1     -   --p       1.8 any cpu
> > Domain-0                             0     2     -   --p       1.7 any cpu
> > Domain-0                             0     3     -   --p       1.6 any cpu
> > Domain-0                             0     4     -   --p       1.4 any cpu
> > Domain-0                             0     5     -   --p       1.4 any cpu
> > Domain-0                             0     6     -   --p       1.5 any cpu
> > Domain-0                             0     7     -   --p       1.3 any cpu
> > dc3                                  1     0     0   -b-      15.2 0
> > dc3                                  1     1     1   -b-       6.8 1
> > dc3                                  1     2     2   -b-       7.5 2
> > dc3                                  1     3     3   -b-       8.0 3
> > After HVM Windows domU shutdown, it stays in ---s- state.
> > root@xen1:/# xm li
> > Name                                        ID   Mem VCPUs      State
> > Time(s)
> > Domain-0                                     0 24106     1     r-----
> > 58.7
> > dc3                                          1  8192     4     ---s--
> > 59.0
> > root@xen1:/# xm vcpu-list
> > Name                                ID  VCPU   CPU State   Time(s) CPU
> > Affinity
> > Domain-0                             0     0     4   r--      48.4 any cpu
> > ...
> > Domain-0                             0     7     -   --p       1.3 any cpu
> > dc3                                  1     0     0   ---      20.0 0
> > dc3                                  1     1     1   ---      10.9 1
> > dc3                                  1     2     2   ---      15.2 2
> > dc3                                  1     3     3   ---      12.9 3
> > The problem goes away if I tell Xen to boot with options dom0_max_vcpus=1
> > dom0_vcpus_pin.
> > What's the difference between Xen boot options to limit vcpus for dom0 to
> > /etc/xen/xend-config.sxp?
> > I am running Xen 3.4.1-rc6 version.
> >
> >
> >
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel
> >
> >

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