From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?ISO-8859-2?Q?Rafa=B3_Bilski?= Subject: Re: Power measurements Date: Sun, 24 Jun 2007 01:57:10 +0200 Message-ID: <467DB356.7050309@interia.pl> References: <200706231544.17062.lenb@kernel.org> <1182634218393@dmwebmail.belize.chezphil.org> Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <1182634218393@dmwebmail.belize.chezphil.org> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: cpufreq-bounces@lists.linux.org.uk Errors-To: cpufreq-bounces+glkc-cpufreq=gmane.org+glkc-cpufreq=gmane.org@lists.linux.org.uk Content-Type: text/plain; charset="iso-8859-9" To: Phil Endecott Cc: cpufreq@lists.linux.org.uk > Len Brown wrote: >> On Saturday 23 June 2007 08:54, Phil Endecott wrote: >>> Dear All, >>> >>> I would like to share some power consumption numbers that I have just >>> measured on my VIA C7-M system. It uses the e_powersaver module and >>> can run at 400MHz or 1.2GHz. I have measured the power consumption >>> when idle and when running a "while(1){}" program at each speed: >>> >>> 400 1200 >>> Idle 16W 16W >>> Busy 17W 20W >>> >>> What I find interesting is that the idle power at 1.2GHz is identical >>> to that at 400 MHz. It isn't. >>> This makes me wonder if the on-demand governor would actually save >>> any power at all. There is a difference of 0,5W~1,0W max. >>> I plan to do some more accurate measurements and to experiment with >>> some different workloads. Has anyone else done anything like this? >> >> In idle, the processor is executing at 0MHz -- >> so idle power consumption has little to do with cpufreq. >=20 > Well, the clock is running so signals will still be toggling in the > processor. Many of them will be gated off though. >=20 > Do other people observe that reducing the clock frequency with cpufreq > does not reduce idle power consumption? Yes. Because of RAM, VGA, harddisk, etc. If I understand correcly You are=20 measuring entire system power consumption. This isn't P4 4GHz which=20 needs 150W. This is VIA C7-Eden 1,2GHz which needs 10W - 50% less is 5W. >> The exception is if the processor doesn't automatically >> adjust it voltage when entering idle. In this case, >> idle power would depend on the frequency of the processor >> when idle was entered -- not because of the frequency -- >> but because of the associated voltage. >=20 > Ah, I had wondered about this. According to sensors, Vcore is always > 1.09 V. (Hmm, I can't be sure that I'm looking at the right line in the > output of the sensors program, or that it is configured correctly. But > none of the voltages change.) Are there any VIA experts reading this > who know what's supposed to happen? % dmesg | grep eps=20 But most C7-Eden doesn't scale voltage. >> I don't know about VIA C7, but some Pentium M's used to >> have different idle power depending on the P-state because >> of this. But the more recent ones all have "Enhanced" C-states >> where the voltage is automatically lowered in idle. >=20 >> back to you question -- 20 - 16W =3D 4W is on the table; >> and the performance difference between 400 and 1200 is on the table. >=20 > Well, in idle, the power difference is zero and the performance > difference is zero. > When active, on-demand would use the higher frequency anyway. > So it looks to me as if 'on-demand' and 'performance' will behave > identically in terms of both power and performance. If CPU is sleeping a lot even 0,5W can make a difference. But there is=20 time needed to enter 400MHz and time needed to leave 400MHz. In real=20 life "performance" governor will use less power. >> how you choose to use these states will depend on how you use >> the machine. >=20 > I don't think there's a situation where I would want to use on-demand. >=20 > Unless I'm missing something. Which is quite likely..... >=20 > Regards, >=20 > Phil. Regards Rafa=B3 =20 -----------------------------------------------------------------------=20 Linda jako gospodyni domowa - zobacz!!! >>> http://link.interia.pl/f1a79