[lkml]   [2012]   [Jan]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
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?


 \ /
  Last update: 2012-01-25 20:59    [W:0.058 / U:5.124 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site