Re: [Powertop] Powertop doesn't detects sleeping ARM cores

On (09/20/12 12:24), Igor Zhbanov wrote:
> Chris Ferron wrote:
> 
> Now I'm looking for solution. But I see now only four ways:
> 
> 1) Develop another kernel mechanism for providing information about all available
>    CPUs and cores. Or ask the kernel authors not to remove offline cores from
>    /proc/cpuinfo and their information files from /sys/.../cpu/.

procps (e.g. top utility) use sysconf _SC_NPROCESSORS_CONF/_SC_NPROCESSORS_ONLN for
that purpose.

https://www.gnu.org/software/libc/manual/html_node/Processor-Resources.html


	-ss

> 2) Scan /sys/.../cpu for all CPUs and temporarily wake it up to gather information.
> 3) Ask the user to run PowerTOP on a heavy loaded system for the first time
>    (or wake up all CPUs by the PowerTOP) and store collected CPU information somewhere
>    in /var/cache/powertop and reuse it on later runs.
> 4) Don't just sleep in a main cycle, but scan /sys/.../cpu for new CPUs to appear.
>    (Perhaps there could be something like D-Bus or netlink notification when a core
>     brought online -- I don't know about it).
> 
> At your personal view, what way fits better in the PowerTOP project?
> 
> P.S. This may be the case for x86 CPUs too. I have disable CPU2 by writing
> to /sys/devices/system/cpu2/online, and the PowerTOP sees only CPU0, CPU1, and CPU3.
> Although default PC's CPU governor as I know doesn't turn off CPUs frequently.
>