From: Mandeep Singh Baines <msb@chromium.org>
To: "David H. Durgee" <dhdurgee@verizon.net>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Request for assistance - excessive kworker CPU wakeups
Date: Wed, 25 Jan 2012 09:44:14 -0800 [thread overview]
Message-ID: <CACBanvpV7pWp07jzuYqzRkbkShvvKvpcu6yFsLfEL+UhT8kp_g@mail.gmail.com> (raw)
In-Reply-To: <4EE27D28.4040909@verizon.net>
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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next prev parent reply other threads:[~2012-01-25 17:44 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-09 21:27 Request for assistance - excessive kworker CPU wakeups David H. Durgee
2012-01-25 17:44 ` Mandeep Singh Baines [this message]
2012-01-25 18:56 ` David H. Durgee
2012-01-25 23:44 ` Mandeep Singh Baines
2012-01-26 0:31 ` David H. Durgee
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