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

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Date:	Fri, 18 Nov 2011 21:33:15 +0100 (CET)
From:	"Nicolas Kalkhof" <nkalkhof@....de>
To:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [REGRESSION] sudden cpu hogging in kernel 3.2 rc-series

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?

Kernel Boot Params: intel_iommu=off i915.i915_enable_rc6=1
Attached: dmesg and kernel .config.

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
CPU_CLK_UNHALT...|
  samples|      %|
------------------
  1515048 99.8101 vmlinux
     1950  0.1285 oprofiled
      356  0.0235 cfbimgblt
      275  0.0181 libc-2.13.so
       73  0.0048 cfbcopyarea
       62  0.0041 libncursesw.so.5.9
       45  0.0030 iwlwifi
       26  0.0017 bash
       25  0.0016 cfbfillrect
       22  0.0014 ld-2.13.so
       16  0.0011 htop
       13 8.6e-04 e1000e
        9 5.9e-04 opreport
        5 3.3e-04 libstdc++.so.6.0.14
        3 2.0e-04 acpid
        1 6.6e-05 ls
        1 6.6e-05 libncurses.so.5.9
        1 6.6e-05 libbfd-2.21.1.so

Regards
Nic

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Download attachment "dmesg.next" of type "application/octet-stream" (51056 bytes)

Download attachment ".config" of type "application/octet-stream" (64419 bytes)