Power Saving

Power Saving

[Stephen Clark]

Hello List,

I am trying to get throttling to work on the following processor with 
linux 2.6.17-1.2142_FC4
with no luck.

AMD Athlon(tm) XP 1700+

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

The /sys/devices/system/cpu/cpu0/cpufreq/* directory does not exist. I 
have modprobed
the following cpufreq* modules.

Module                  Size  Used by
cpufreq_stats           6101  0
cpufreq_powersave       2241  0
cpufreq_ondemand        7009  0
cpufreq_conservative     7265  0


What am I doing wrong?

Thanks Steve

-- 

"They that give up essential liberty to obtain temporary safety, 
deserve neither liberty nor safety."  (Ben Franklin)

"The course of history shows that as a government grows, liberty 
decreases."  (Thomas Jefferson)

Re: Power Saving

[Dave Jones]

On Mon, Nov 19, 2007 at 07:41:31PM -0500, Stephen Clark wrote:
 > Hello List,
 > 
 > I am trying to get throttling to work on the following processor

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)

 > with linux 2.6.17-1.2142_FC4 with no luck.

wow. that's a prehistoric kernel.

 > AMD Athlon(tm) XP 1700+

you lose.  Only the mobile athlons supported scaling their speed.
And even then, only if the BIOS supported it with the correct tables.
(Typically this means, "only laptops").

	Dave

-- 
http://www.codemonkey.org.uk

Re: Power Saving

[Stephen Clark]

Dave Jones wrote:

>On Mon, Nov 19, 2007 at 07:41:31PM -0500, Stephen Clark wrote:
> > Hello List,
> > 
> > I am trying to get throttling to work on the following processor
>
>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)
>
> > with linux 2.6.17-1.2142_FC4 with no luck.
>
>wow. that's a prehistoric kernel.
>
> > AMD Athlon(tm) XP 1700+
>
>you lose.  Only the mobile athlons supported scaling their speed.
>And even then, only if the BIOS supported it with the correct tables.
>(Typically this means, "only laptops").
>
>	Dave
>
>  
>
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%

and:
[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]

????
Steve

-- 

"They that give up essential liberty to obtain temporary safety, 
deserve neither liberty nor safety."  (Ben Franklin)

"The course of history shows that as a government grows, liberty 
decreases."  (Thomas Jefferson)

Re: Power Saving

[Dave Jones]

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

-- 
http://www.codemonkey.org.uk

Re: Power Saving

[H. Peter Anvin]

Dave Jones wrote:
>  > 
>  > 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.
> 

And more importantly, there is no power advantages over T states as 
opposed to C states.  They pretty much mean pulsing the system in and 
out of either C1 or C2 depending on the CPU/chipset.

	-hpa

Re: Power Saving

[Phillip Susi]

H. Peter Anvin wrote:
> And more importantly, there is no power advantages over T states as 
> opposed to C states.  They pretty much mean pulsing the system in and 
> out of either C1 or C2 depending on the CPU/chipset.

Well, they FORCE the use of the C states to save power, even if the 
kernel doesn't want to because it still has runnable tasks.  This can be 
useful if you know you are running a task that busy waits but would not 
suffer from having the performance of the cpu cut in half.  Since it is 
busy waiting, the kernel never activates the C states, but the 
throttling will force it and thus, save you power and heat.