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    SubjectRe: Request for assistance - excessive kworker CPU wakeups
    From
    On Fri, Dec 9, 2011 at 1:27 PM, David H. Durgee <dhdurgee@verizon.net> wrote:
    > I recently purchased a Lenovo IdeaPad Z560, model 09143YU, and as I am not a
    > Windows fan I installed Linux Mint 11 Katya x64 to use instead of the
    > supplied W7.  I was encountering a known hang and had to upgrade to a later
    > kernel, so I am now using the 2.6.38-11-generic #50-Ubuntu SMP Mon Sep 12
    > 21:17:25 UTC 2011 x86_64 kernel.
    >
    > I had my first occasion to use the laptop for an extended period for the
    > first time over the Thanksgiving holiday and I found it needed to be tuned.
    >  I downloaded powertop and used it to discover where my problems were.
    >  After addressing excessive i915 interrupts due to DRI the next most
    > frequent cause of CPU wakeups is a kworker on the system.  A search lead to
    > a post by Tejun, indicating the need to trace such issues. Running the trace
    > showed that 1933 of 2748 events were of the form:
    >
    > <idle>-0     [000] 22005.355346: workqueue_queue_work: work
    > struct=ffff8800bb411188 function=do_dbs_timer workqueue=ffff88012b5d2c00
    > req_cpu=0 cpu=0
    >
    > Tejun indicated that this is a workitem used by cpufreq and likely caused by
    > something else hitting the CPU frequently.  So how do I diagnose this
    > further and isolate the cause for correction?
    >
    > If you would like a summary of this, download this spreadsheet:
    >
    > http://home.comcast.net/%7Eddurgee/Tracelog.ods
    >
    > If you would like to inspect the trace log itself:
    >
    > http://home.comcast.net/%7Eddurgee/tracelog.zip
    >

    Hi Dave,

    I don't know the cpufreq code that well, but it seem that this
    workqueue is schedule periodically. You
    can examine the sampling rate via /sys:

    $ grep "" /sys/devices/system/cpu/cpufreq/ondemand/sampling_rate*

    Just curious, are you running nohz:

    $ dmesg | grep -i nohz

    Regards,
    Mandeep

    > Dave
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