Re: Power Saving

Dave Jones
2007-11-20T01:12:52Z

On Mon, Nov 19, 2007 at 08:05:29PM -0500, Stephen Clark wrote:

> >I think by throttling, you actually mean changing frequency/voltage ?
> >(throttling is something else, where the CPU skips every n cycles,
> > which doesn't actually save any power)
> >
> well what about the info from /proc/
>
> cat /proc/acpi/processor/CPU0/info
> processor id: 0
> acpi id: 0
> bus mastering control: no
> power management: yes
> throttling control: yes
> limit interface: yes
>
> and:
> cat /proc/acpi/processor/CPU0/throttling
> state count: 2
> active state: T0
> states:
> *T0: 00%
> T1: 50%

See above. These are throttling states, used typically
if the system is overheating.

> [root@joker ~]# cat /proc/acpi/processor/CPU0/power
> active state: C2
> max_cstate: C8
> bus master activity: d18324c9
> states:
> C1: type[C1] promotion[C2] demotion[--]
> latency[000] usage[01340140]
> *C2: type[C2] promotion[--] demotion[C1]
> latency[090] usage[02980043]
>
> ????

C states are unrelated to frequency/voltage scaling (which are P states)
They get taken advantage of automatically by ACPI as you can
see from the usage fields.

Dave

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