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    SubjectRe: Request for assistance - excessive kworker CPU wakeups
    Mandeep Singh Baines wrote:
    > On Fri, Dec 9, 2011 at 1:27 PM, David H. Durgee<> 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:
    >> If you would like to inspect the trace log itself:
    > 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
    dhdurgee@DHD-Z560 ~/Downloads $ grep ""
    dhdurgee@DHD-Z560 ~/Downloads $ dmesg | grep -i nohz
    dhdurgee@DHD-Z560 ~/Downloads $

    Does this explain what I am seeing? Does this square with the
    observations in my spreadsheet? Does this suggest a means of reducing
    these excessive wakeups? Is there more information I can provide to
    suggest a course of action?


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