Messages in this thread | | | Date | Wed, 25 Jan 2012 09:44:14 -0800 | Subject | Re: Request for assistance - excessive kworker CPU wakeups | From | Mandeep Singh Baines <> |
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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
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