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Subjectexcessive kworker CPU wakeups
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, who is cc'd, 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?

Dave


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