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

Sergey Senozhatsky wrote:

> On (09/20/12 13:29), Igor Zhbanov wrote:
>>> 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
>> Counting of the CPUs is the least problem. (By the way, how sysconf() figures
>> out the number? I suppose that it reads /proc/cpuinfo of scans /sys/.
>> Is there any other way?).
>>
>> The problem is that the PowerTOP needs to read information about cores
>> from the files in /sys/.../cpu/cpuX/ directory (about C- and P-states, siblings
>> etc). And needed files in these directories are present only for cores
>> which are currently online.
> right, I was thinking about that some time ago: and from the top of my head kind of a solution
> seemed to be to track number of CPUs before measure, compare with the previously known one,
> and "re-init" powertop (at least rebuild CPUs part), but it's not that often that I offline/online
> CPUs, so I decided to drop it. with ARM we have a different story.
>
> on x86(_64) "dirty" CPU offline support looks "easy", just make get_msr() error non-fatal.
> online -- that's the problem, agree.

Perhaps PowerTOP could wake up every core in its calibration phase and story collected
information in platform config file.

-- 
Best regards,
Igor Zhbanov,
Expert Software Engineer,
phone: +7 (495) 797 25 00 ext 3806
e-mail: i.zhbanov(a)samsung.com

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