linux-kernel - Re: power increase issue on light load

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Date:	Fri, 1 Jul 2011 11:00:07 -0700
From:	Nikhil Rao <ncrao@...gle.com>
To:	Ming Lei <tom.leiming@...il.com>
Cc:	"Alex,Shi" <alex.shi@...el.com>, peterz@...radead.org,
	mingo@...e.hu, "Chen, Tim C" <tim.c.chen@...el.com>,
	"Li, Shaohua" <shaohua.li@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: power increase issue on light load

Hi Ming,

On Thu, Jun 30, 2011 at 10:44 PM, Ming Lei <tom.leiming@...il.com> wrote:
> Hi,
>
> On Thu, Jun 23, 2011 at 10:43 AM, Alex,Shi <alex.shi@...el.com> wrote:
>> commit c8b281161dfa4bb5d5be63fb036ce19347b88c63 causes light load
>> benchmark use more than 10% system power on platform NHM-EP and laptop
>> Thinkpad T410 etc. The benchmarks are specpower and bltk office.
>>
>> I tried to track this issue, but only find deep C sate time reduced
>> much, about from 90% to 30~40%, the C0 or C1 state increase much on
>> different machines.
>>
>> Powertop just hints RES interrupts has a bit more. but when I try "perf
>> probe native_smp_send_reschedule". I didn't find much.
>
> I see the problem on -rc5 in my T410 too, the fan has been ringing always
> and powertop reports "Wakeups-from-idle per second : 508.6".
>

Thanks for reporting this issue. Looks like the increased resolution
has a negative impact on power savings balance. I'm looking into this
issue based on Alex's data, but If you can give a trace or something
that I can work with it will be really helpful.

-Thanks,
Nikhil
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