linux-kernel - RE: Increased ipw2200 power usage with dynticks

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Message-ID: <653FFBB4508B9042B5D43DC9E18836F5EA4D36@scsmsx415.amr.corp.intel.com>
Date:	Mon, 21 May 2007 10:24:15 -0700
From:	"Pallipadi, Venkatesh" <venkatesh.pallipadi@...el.com>
To:	Björn Steinbrink <B.Steinbrink@....de>,
	"Andi Kleen" <andi@...stfloor.org>,
	"Brown, Len" <len.brown@...el.com>
Cc:	<tglx@...utronix.de>, <mingo@...e.hu>,
	"Zhu, Yi" <yi.zhu@...el.com>, <linux-kernel@...r.kernel.org>,
	<arjan@...radead.org>, <trenn@...e.de>
Subject: RE: Increased ipw2200 power usage with dynticks

 

>-----Original Message-----
>From: Björn Steinbrink [mailto:B.Steinbrink@....de] 
>Sent: Monday, May 21, 2007 12:50 AM
>To: Andi Kleen
>Cc: tglx@...utronix.de; mingo@...e.hu; Zhu, Yi; 
>linux-kernel@...r.kernel.org; arjan@...radead.org; Pallipadi, 
>Venkatesh; trenn@...e.de
>Subject: Re: Increased ipw2200 power usage with dynticks
>
>On 2007.05.20 20:55:35 +0200, Andi Kleen wrote:
>> Björn Steinbrink <B.Steinbrink@....de> writes:
>> > 
>> > Ok, it seems that ipw2200 is just a trigger for the 
>problem here. AFAICT
>> > the cause of the worse C state usage is that after ipw2200 
>has woken the
>> > cpu, acpi_processor_idle() chooses C2 (due to dma? bm? I have no
>> > idea...) as the prefered sleep state. Now without NO_HZ or 
>when I hold
>> > down a key, there are interrupts that wake up the CPU and when
>> > acpi_processor_idle() is called again the promotion to 
>C3/C4 happens.
>> > But with NO_HZ, there are no such interrupts, most wakeups 
>are caused by
>> > ipw2200 and so the processor doesn't go any deeper than C2 
>most of the
>> > time and thus wastes lots of power.
>> 
>> The cpuidle governour code Venki is working on is supposed 
>to address this.
>> There have been also earlier prototype patches by Adam Belay and
>> Thomas Renninger.
>
>Venki (at least I think it was him) also told me about cpuidle and the
>menu governor on #powertop. Unfortunately, cpuidle seems to be 
>gone from
>acpi-test (or I'm simply still too stupid for git/gitweb). I manually
>added the cpuidle and menu governor patches on top of my 
>2.6.22-rc1-hrt8
>kernel, but that broke C-state duration accounting.
>
>On the bright side of things is power usage though, which is down to an
>incredible 13.9W in idle+ipw2200 :)
>

Nice to hear that cpuidle-menu governor gets 13.9W :-).
Powertop will need some changes to go with cpuidle, but that should be simple.

We need some more testing for cpuidle before it gets into git.
Len: Looks like cpuidle got dropped out of mm again. Can you merge it back it please.

Thanks,
Venki
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