linux-kernel - Re: Too many poll_idle cpu calls in kernel 3.2 rc-series

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Date:	Mon, 28 Nov 2011 21:31:13 +0100 (CET)
From:	"Nicolas Kalkhof" <nkalkhof@....de>
To:	"Andi Kleen" <andi@...stfloor.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Too many poll_idle cpu calls in kernel 3.2 rc-series

Andi,

correct. The issue was introduced somewhere between 3.1 final and 3.2-rc1. I've tried to track down the bad commit but so far I haven't been successfull. The only workaround I found is to set the idle boot parameter to mwait and to disable CONFIG_INTEL_IDLE. Somehow the kernel seems to set idle to poll by default - no idea why :-(. I wonder if other mobile sandy bridge cpus are affected as well.

Regards,
Nic

-----Ursprüngliche Nachricht-----
Von: "Andi Kleen" <andi@...stfloor.org>
Gesendet: Nov 28, 2011 8:33:28 PM
An: "Nicolas Kalkhof" <nkalkhof@....de>
Betreff: Re: Too many poll_idle cpu calls in kernel 3.2 rc-series

>"Nicolas Kalkhof" <nkalkhof@....de> writes:
>
>> the kernel v3.2 series shows excessive poll_idle calls during system idle phases causing the cpu
>> (mobile i7 2620M) to heat up and draw additional 10% more power.  All kernel versions between
>> 3.2-rc1 and 3.2-rc3 are affected. Perf Top and Powertop both show the same issue.
>> I've posted a similar bug report before: http://marc.info/?l=linux-kernel&m=132164909313594&w=2
>> and used perf top -U to verify the poll_idle calls as requested.
>
>So it didn't happen with earlier kernels?
>I would suggest a git bisect in this case.
>
>-Andi
>
>--
>ak@...ux.intel.com -- Speaking for myself only
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