Pkg xen devel - Jul 2012 - Bug#683170: Xend causing high CPU load - starting domU failing

Package: xen-utils-4.0
Version: 4.0.1-5.2

After clean upgrade from Lenny I got xend highly use CPU resources 
causing domU don't being created - due to timeouts for vifs and vbds 
(mostly CPU Steal Time was increasing - no iowaits).
Tried Xen boot options acpi=noirq|ht without success. Option acpi=off 
solved that issue, but performance of the server was horrible. The final 
workaround was to set dom0-cpus to 1 in /etc/xen/xend-config.sxp.
This setting is causing the dynamic changes are not propagated to domUs 
(e.g. increasing memory).
Unfortunately setting that option back to 0 and restarting xend will not 
unpause dom0's vcpus.
I tested the system without booting Xen and everything was working like 
a charm.

server1:~# xm vcpu-list 0
Name                                ID  VCPU   CPU State   Time(s) CPU 
Affinity
Domain-0                             0     0     0   r--    1568.2 0
Domain-0                             0     1     -   --p     129.3 0
Domain-0                             0     2     -   --p     132.1 0
Domain-0                             0     3     -   --p     134.8 0

server1:~# uname -a
Linux server1 2.6.32-5-xen-amd64 #1 SMP Sun May 6 08:57:29 UTC 2012 
x86_64 GNU/Linux

server1:~# xm info
host                   : server1
release                : 2.6.32-5-xen-amd64
version                : #1 SMP Sun May 6 08:57:29 UTC 2012
machine                : x86_64
nr_cpus                : 4
nr_nodes               : 1
cores_per_socket       : 4
threads_per_core       : 1
cpu_mhz                : 2128
hw_caps                : 
bfebfbff:20000800:00000000:00000940:0000e3bd:00000000:00000001:00000000
virt_caps              : hvm
total_memory           : 8189
free_memory            : 1996
node_to_cpu            : node0:0-3
node_to_memory         : node0:1996
node_to_dma32_mem      : node0:1991
max_node_id            : 0
xen_major              : 4
xen_minor              : 0
xen_extra              : .1
xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p hvm-3.0-x86_32 
hvm-3.0-x86_32p hvm-3.0-x86_64
xen_scheduler          : credit
xen_pagesize           : 4096
platform_params        : virt_start=0xffff800000000000
xen_changeset          : unavailable
xen_commandline        : placeholder dom0_mem=756M acpi=noirq numa=off 
loglvl=all guest_loglvl=all
cc_compiler            : gcc version 4.4.5 (Debian 4.4.5-8)
cc_compile_by          : fw
cc_compile_domain      : deneb.enyo.de
cc_compile_date        : Thu Jun 21 06:41:09 UTC 2012
xend_config_format     : 4


Regards,
--
Peter Viskup