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

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Message-ID: <4ED4BCD5.3090308@linux.vnet.ibm.com>
Date:	Tue, 29 Nov 2011 16:37:01 +0530
From:	Deepthi Dharwar <deepthi@...ux.vnet.ibm.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	Nicolas Kalkhof <nkalkhof@....de>, linux-kernel@...r.kernel.org,
	Linux PM mailing list <linux-pm@...r.kernel.org>
Subject: Re: Too many poll_idle cpu calls in kernel 3.2 rc-series

On 11/29/2011 02:14 AM, Andi Kleen wrote:

> On Mon, Nov 28, 2011 at 09:31:13PM +0100, Nicolas Kalkhof wrote:
>> 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.
> 
> There are only a few changesets affecting drivers/idle
> 
> Can you try to git revert 
> 
> 46bcfad7a819bd17ac4e831b04405152d59784ab
> 4202735e8ab6ecfb0381631a0d0b58fefe0bd4e2
> e978aa7d7d57d04eb5f88a7507c4fb98577def77
> 
> ?
> 
> -Andi


Hi,

I am guessing that for workaround just setting the idle boot parameter
to mwait should work. Have u tested this without disabling
CONFIG_INTEL_IDLE ?

Also one thing to note from your logs is, cpu is not entering any of the
other C states except for POLL. Can you also check if your are enabling
only POLL for idle. I am able to enter deeper C-states on i5-2540M with
Intel_Idle enabled.

Power top o/p:
-------------

            Core    |             CPU 0               CPU 1
POLL        0.0%    | POLL        0.0%    0.0 ms      0.0%    0.0 ms
C1-SNB      1.4%    | C1-SNB      2.2%    0.7 ms      0.5%    0.9 ms
C3-SNB      0.9%    | C3-SNB      1.6%    1.2 ms      0.1%    1.2 ms
C6-SNB      0.2%    | C6-SNB      0.3%    1.6 ms      0.0%    0.9 ms
C7-SNB     95.8%    | C7-SNB     93.7%    3.7 ms     97.8%   15.1 ms


Regards,
Deepthi

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