Re: [REGRESSION] sudden cpu hogging in kernel 3.2 rc-series

[Nicolas Kalkhof]

This happens on my machine after some minutes, too when running X and the trinity desktop. the cpu continuously uses up additional ~10 watts comparing to older 3.1 kernels. The issue remains high even after I kill X. A closer investigation shows that poll_idle uses up the cpu (see dump below). Is it normal for poll_idle to use up all ressources?

CPU: Intel Sandy Bridge microarchitecture, speed 2.701e+06 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (No unit mask) count 100000
samples % app name symbol name
524625ÂÂ 96.8279Â vmlinuxÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ poll_idle
7807ÂÂÂÂÂ 1.4409Â cfbimgbltÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ /cfbimgblt
813ÂÂÂÂÂÂ 0.1501Â vmlinuxÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ rb_get_reader_page
806ÂÂÂÂÂÂ 0.1488Â vmlinuxÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ fbcon_redraw.clone.30
616ÂÂÂÂÂÂ 0.1137Â vmlinuxÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ i8042_interrupt
454ÂÂÂÂÂÂ 0.0838Â vmlinuxÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ bit_putcs
414ÂÂÂÂÂÂ 0.0764Â vmlinuxÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ ring_buffer_consume
373ÂÂÂÂÂÂ 0.0688Â vmlinuxÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ _cond_resched
301ÂÂÂÂÂÂ 0.0556Â cfbcopyareaÂÂÂÂÂÂÂÂÂÂÂÂÂ /cfbcopyarea
277ÂÂÂÂÂÂ 0.0511Â libstdc++.so.6.0.14ÂÂÂÂÂ /usr/lib64/gcc/x86_64-pc-linux-gnu/4.5.3/libstdc++.so.6.0.14
239ÂÂÂÂÂÂ 0.0441Â cfbfillrectÂÂÂÂÂÂÂÂÂÂÂÂÂ /cfbfillrect
....

Regards
Nic

-----UrsprÃngliche Nachricht-----
Von: "Maciej Rutecki" <maciej.rutecki@xxxxxxxxx>
Gesendet: Nov 21, 2011 10:11:17 PM
An: "Nicolas Kalkhof" <nkalkhof@xxxxxx>
Betreff: Re: [REGRESSION] sudden cpu hogging in kernel 3.2 rc-series

>On piÄtek, 18 listopada 2011 o 21:33:15 Nicolas Kalkhof wrote:
>> Hello,
>>
>> since the merges for kernel 3.2 came in late october, my mobile i7 2620M
>> sandybridge cpu/gpu seems to run hotter (approx 10 ÂC) when idling and
>> after some minutes according to top the cpu load goes up on all cores but
>> the cpu frequency stays low (800 MHz) as well as the gpu (650MHz) and the
>> system is responding well. Yet still additional 5-8 watts are continously
>> drained from the power supply. Something is throttling up :(. Oprofile
>> shows that the kernel hogs the cpu (see dump below). This happens with
>> every kernel since the 3.2 merge window closed up to latest linux-next. I
>> wasn't able to track the bad commit down yet.
>>
>> Could someone please confirm the issue?
>>
>
>I observed similar behaviour, few minutes after boot, when KDE is working
>plasma-desktop process (sometimes another) uses 20-50% cpu. System and kernel
>works without any kernel, but cpu usage is greater than in 3.1 (and older).
>
>Hardware: old hp/compaq nx6310
>
>Add this mail to regression list.
>
>Regards
>--
>Maciej Rutecki
>http://www.mrutecki.pl


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