get_vcpu_total in nova/virt/libvirt.py reports wrong number of physical CPUs on Xen dom0 systems

[Christian Berendt]

The Xen dom0 has 4 physical CPUs assigned, multiprocessing.cpu_count() only sees those CPUs.

But the system has 32 physical CPUs. While using virsh nodeinfo you can receive the correct number of CPUs.

Because we're in the libvirt driver we should use libvirt and not multiprocessing.

Python 2.6.8 (unknown, May 29 2012, 22:30:44)
[GCC 4.3.4 [gcc-4_3-branch revision 152973]] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import multiprocessing
>>> print multiprocessing.cpu_count()
4

# cat /proc/cpuinfo | grep processor | wc -l
4

# virsh nodeinfo
CPU model: x86_64
CPU(s): 32
CPU frequency: 2000 MHz
CPU socket(s): 4
Core(s) per socket: 8
Thread(s) per core: 1
NUMA cell(s): 1
Memory size: 402648064 KiB

# xm cpupool-list
Name CPUs Sched Active Domain count
Pool-0 32 credit y 1

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/17125

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/17125
Committed: http://github.com/openstack/nova/commit/16cb60ce661f00f9a91c8ad02c381d2f9c504580
Submitter: Jenkins
Branch: master

commit 16cb60ce661f00f9a91c8ad02c381d2f9c504580
Author: Christian Berendt <email address hidden>
Date: Thu Nov 29 18:03:02 2012 +0100

    use libvirt getInfo() to receive number of physical CPUs

    multiprocessing.cpu_count() reports the wrong number of
    physical CPUs on a Xen dom0 system. Because we're inside
    the libvirt virtualization driver the corresponding
    libvirt method (getInfo()) should be used instead.

    fixes bug 1084611

    Change-Id: Ida4be889ce98c7a6f58564a8bc295b360ff65965