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xen-devel
Re: AW: [Xen-devel] How to use Px/Cx for power saving?
Hi, Kevin
Thank you for your infomation.
Tian, Kevin wrote:
Which version are you using? In latest Xen unstable, Xen controlled
cpufreq is always enabled with userspace governor as the default.
In such case, you could use xenpm to manually change frequency
(xenpm set-scaling-speed). Then "xenpm set-scaling-governor"
can be used to choose a new governor like ondemand in the fly.
Before 18950, cpufreq is by default disabled, and you have to add
'cpufreq=xen' in grub to activate xen controlled cpufreq logic. In
either case, CONFIG_CPU_FREQ in dom0 is not required.
Oh, I used cset:18942.
'cpufreq=dom0-kernel' can be always used to allow dom0 control
freq directly. In such case, Xen itself exits the game, and then you
have to follow below trick to enable CONFIG_CPU_FREQ in dom0
kernel.
If dom0_max_vcpus < total_phys_cpus, dom0 control only his cpus.
So other cpus don't enter px/cx state, right?
And you recommend cpufreq=xen?
For cpuidle, you need a similar boot option 'cpuidle' in xen cmdline
which is off by default. We have plan to allow in-the-fly on/off from
xenpm too.
Thanks.
One of our engineer is working on document side, including all
relevant options and xenpm usage. We tempt to place it on Xen
wiki first, and will let you know for comments. :-)
Great! It will be very helpful.
Best Regards,
Akio Takebe
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