lkml.org 
[lkml]   [2013]   [Sep]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [Query-CPUIdle]: Not much activity in C0 state
On 08/27/2013 12:23 PM, Viresh Kumar wrote:
> Hi Guys,
>
> I was trying to run following on my thinkpad:
>
> watch -n1 cat /sys/devices/system/cpu/cpu*/cpuidle/state*/usage
>
> I can see lots of activities on State 1-4, but not much on state 0..
> I thought we should enter this state as soon as we come out to
> non-idle state.. And so this count must be changing quite rapidly.
>
> Is this a bug?

Hi Viresh,

the menu governor tries always to stick to C1 (state1) as default state,
look at the menu_select function. The state0 (not C0 but 'poll') will
happen when the next timer event is less than 5us, this occurs rarely.
You can easily spot it by doing while $(true); usleep 2; done

The poll state is x86 specific where the cpu detects the 'rep nop'
instructions to do some power saving.

Hope that helps

-- Daniel



--
<http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs

Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2013-09-03 16:01    [W:0.036 / U:0.832 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site