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

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
524625   96.8279  vmlinux                  poll_idle
7807      1.4409  cfbimgblt                /cfbimgblt
813       0.1501  vmlinux                  rb_get_reader_page
806       0.1488  vmlinux                  fbcon_redraw.clone.30
616       0.1137  vmlinux                  i8042_interrupt
454       0.0838  vmlinux                  bit_putcs
414       0.0764  vmlinux                  ring_buffer_consume
373       0.0688  vmlinux                  _cond_resched
301       0.0556  cfbcopyarea              /cfbcopyarea
277       0.0511  libstdc++.so.6.0.14      /usr/lib64/gcc/x86_64-pc-linux-gnu/4.5.3/libstdc++.so.6.0.14
239       0.0441  cfbfillrect              /cfbfillrect


Regards
Nic

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

On piątek, 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 °C) 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

___________________________________________________________
SMS schreiben mit WEB.DE FreeMail - einfach, schnell und
kostenguenstig. Jetzt gleich testen! http://f.web.de/?mc1192
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/