RE: [linux-pm] [PATCH] cpuidle: avoid singing capacitors

[Pallipadi, Venkatesh]

>-----Original Message-----
>From: linux-kernel-owner@xxxxxxxxxxxxxxx 
>[mailto:linux-kernel-owner@xxxxxxxxxxxxxxx] On Behalf Of Pierre Ossman
>Sent: Thursday, March 13, 2008 9:35 AM
>To: Len Brown
>Cc: linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx; Pavel Machek; LKML; 
>Adam Belay; Andi Kleen; Lee Revell
>Subject: Re: [linux-pm] [PATCH] cpuidle: avoid singing capacitors
>
>On Wed, 12 Mar 2008 15:11:17 -0400
>Len Brown <lenb@xxxxxxxxxx> wrote:
>
>> > 
>> > So for now, the only viable workaround is processor.max_cstate....
>> 
>> yup, that's why we put it in.  Is it insufficient?
>> 
>
>For some value of insufficient. It is sub-optimal. I'm hoping 
>there is a way to enter C3 in a pattern that avoids the noise 
>and still gives a reduced power usage.
>

Can you try using /dev/cpu_dma_latency from an user space application.
Refer Documentation/pm_qos_interface.txt for usage. With this interface
you can change menu governor behavior from userspace, by dynamically
allowing it to use C3 or not. I am thinking that something like allowing
C3 for few seconds and blocking it for few seconds may help.

Thanks,
Venki
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