[CentOS] Questions on cpu frequency scaling AMD vs. Intel
maillists at conactive.com
Sun Aug 3 18:06:09 UTC 2008
Kai Schaetzl wrote on Sun, 03 Aug 2008 16:31:19 +0200:
> Actually, not the latest kernel. The CentOS xen boot (hypervisor) kernel
> /xen.gz-2.6.18-92.1.6.el5 (and maybe earlier) ones calculates the frequency
> correct, the Xen 3.2 boot kernel (xen.gz-3.2) from the Xen 3.2 package
> offered at xen.org does not. Might there be a kernel parameter or other
> measure that could correct this?
After some more research I have found the correct incantation for this. The
CentOS/RH kernels seem to have this enabled by default, the kernels from
xen.org have to be "enabled" with a command-line option to the hypervisor-
kernel (not the CentOS kernel).
kernel /xen.gz-3.2 cpufreq=dom0-kernel
I'm getting now correct readings of the frequencies. And scaling up on demand
works. At least in dom0. I'm not so sure if it works for domUs as well. A
quick test showed no ondemand scaling in dom0 when running a cpu-intensive
task in a domU. Anyone has more experience with this?
Kai Schätzl, Berlin, Germany
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