* [Query-CPUIdle]: Not much activity in C0 state
@ 2013-08-27 10:23 Viresh Kumar
2013-09-03 13:32 ` Daniel Lezcano
0 siblings, 1 reply; 2+ messages in thread
From: Viresh Kumar @ 2013-08-27 10:23 UTC (permalink / raw)
To: Rafael J. Wysocki, Daniel Lezcano
Cc: linux-pm@vger.kernel.org, Linux Kernel Mailing List,
Lists linaro-kernel, Suresh.Srinivasan, Amit Kucheria,
Sudeep KarkadaNagesha
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?
--
viresh
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [Query-CPUIdle]: Not much activity in C0 state
2013-08-27 10:23 [Query-CPUIdle]: Not much activity in C0 state Viresh Kumar
@ 2013-09-03 13:32 ` Daniel Lezcano
0 siblings, 0 replies; 2+ messages in thread
From: Daniel Lezcano @ 2013-09-03 13:32 UTC (permalink / raw)
To: Viresh Kumar
Cc: Rafael J. Wysocki, linux-pm@vger.kernel.org,
Linux Kernel Mailing List, Lists linaro-kernel, Suresh.Srinivasan,
Amit Kucheria, Sudeep KarkadaNagesha
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
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2013-09-03 13:32 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2013-08-27 10:23 [Query-CPUIdle]: Not much activity in C0 state Viresh Kumar
2013-09-03 13:32 ` Daniel Lezcano
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).