[CentOS-virt] Power Management and dom0 cpus

Tue Jul 27 16:30:33 UTC 2010
Ben M. <centos at rivint.com>

["Standard" CentOS 5.5 Xen Virtualization installation.]

I'm setting up a new box on AMD Opteron platform.

I'm doing some preliminary baselines (no domUs running) with an inline 
Watt/VA meter.

It appears to enable full power management Xen dom0 must have all cpus 
by not limiting in kernel statement nor in xendconfig.sxp. In previous 
installations I cut them back to 1 or 2.

The bonus of all cpus appears to be a 16% to 20% reduction in wattage/va 
consumption at idle. Pretty substantial when I consider that my electric 
utility rates have increased 75% (yep) in the past two years alone.

My question is to anyone with experience with this is will I be seeing a 
significant performance hit on domU performance in either 
paravirtualized or fully virtualized guests (or both)?