Xen users - Jun 2011 - annoying 2 - 3 second lag every few minutes in Windows XP VM on Debian 6 Squeeze

Hi,

I don''t know if this is a known issue, but I couldn''t find any
references to it online, so I figured I''d start a topic here.

I am running Debian 6 (Squeeze), and have the standard Debian 6 Xen 
kernel and all the Xen support tools and packages that come from 
Squeeze. I''ve created a Xen VM on the local disk:

- dd if=/dev/zero of=somefile bs=1024k count=4000 to create the disk
- Installed Windows XP sp3 from an ISO file (standard installation with 
no extras).

After booting into Windows, without any updates or anything running in 
windows, I am observing a 2 - 3 second lag or freeze or whatever you 
want to call it every few minutes. This happens no matter whether I am 
running a "local console", or connecting via VNC to the virtual
machine.
During the freeze, I''ve got ssh shells and lots of stuff open on the 
server, and everything is running, so it''s not the connection. Also,
the
machine is not on a remote server, so it''s not NFS or something like
that.

While running top, I observe that during the freeze, all of the 
Xen-related processes drop off the list (i.e. do not take up any 
CPU-time). There are no tell-tale dmesg messages. Here are some details 
of the system:

Supermicro H8DGU-F motherboard, 2x Magny-cours CPU with 12 cores each, 
64GB of RAM. uname -a reports:

Linux vsrv1 2.6.32-5-xen-amd64 #1 SMP Thu May 19 01:16:47 UTC 2011 
x86_64 GNU/Linux

The reason I am certain this is a Xen issue, is that running the exact 
same VM image with qemu-kvm produces no such effect.

Many thanks for any input and/or workarounds!

Iordan Iordanov

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Hi,

Have you tried a vm with the pv drivers installed?

What about Linux vms? 

Ian

On 10 Jun 2011, at 19:15, "Iordan Iordanov"
<iordan@cdf.toronto.edu> wrote:
> Hi,
> 
> I don''t know if this is a known issue, but I couldn''t
find any references to it online, so I figured I''d start a topic here.
> 
> I am running Debian 6 (Squeeze), and have the standard Debian 6 Xen kernel
and all the Xen support tools and packages that come from Squeeze. I''ve
created a Xen VM on the local disk:
> 
> - dd if=/dev/zero of=somefile bs=1024k count=4000 to create the disk
> - Installed Windows XP sp3 from an ISO file (standard installation with no
extras).
> 
> After booting into Windows, without any updates or anything running in
windows, I am observing a 2 - 3 second lag or freeze or whatever you want to
call it every few minutes. This happens no matter whether I am running a
"local console", or connecting via VNC to the virtual machine. During
the freeze, I''ve got ssh shells and lots of stuff open on the server,
and everything is running, so it''s not the connection. Also, the
machine is not on a remote server, so it''s not NFS or something like
that.
> 
> While running top, I observe that during the freeze, all of the Xen-related
processes drop off the list (i.e. do not take up any CPU-time). There are no
tell-tale dmesg messages. Here are some details of the system:
> 
> Supermicro H8DGU-F motherboard, 2x Magny-cours CPU with 12 cores each, 64GB
of RAM. uname -a reports:
> 
> Linux vsrv1 2.6.32-5-xen-amd64 #1 SMP Thu May 19 01:16:47 UTC 2011 x86_64
GNU/Linux
> 
> The reason I am certain this is a Xen issue, is that running the exact same
VM image with qemu-kvm produces no such effect.
> 
> Many thanks for any input and/or workarounds!
> 
> Iordan Iordanov
> 
> _______________________________________________
> Xen-users mailing list
> Xen-users@lists.xensource.com
> http://lists.xensource.com/xen-users
> 

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Hi Ian,

On 06/10/11 14:22, Ian Tobin wrote:
> Hi,
>
> Have you tried a vm with the pv drivers installed?
Just a follow-up. I never got to installing the vm and pv drivers. Are 
they any use? We won''t be using Windows much, but it would be nice if
we
get a benefit.

Aside from that, I decided to pull in Sid''s package into Squeeze and 
build it, and with Xen 4.1, the annoying 2 - 3 second lag seems to have 
disappeared.

Cheers,
Iordan

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