linux-kernel - Re: [PATCH 7/7] ondemand: Solve the big performance issue with ondemand during disk IO

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Message-ID: <20100424045626.GA7561@elf.ucw.cz>
Date:	Sat, 24 Apr 2010 06:56:26 +0200
From:	Pavel Machek <pavel@....cz>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	mingo@...e.hu, peterz@...radead.org, tglx@...utronix.de,
	davej@...hat.com, cpufreq@...r.kernel.org
Subject: Re: [PATCH 7/7] ondemand: Solve the big performance issue with
 ondemand during disk IO

Hi!

> > Well, and now, if you do something like cat /dev/<your usb1.1 hdd> >
> > /dev/null, you'll keep cpu on max frequency. Not a problem for new
> > core i7, but probably big deal for athlon 64.
> 
> do you have facts not speculation for this? Does the athlon 64 really
> keep its voltage high during idle? That would surprise me greatly...

So... some old data. It is not exactly athlon 64 -- I don't have that
particular number for it -- but: (from my old notes):

evo n620c [63.3 Wh]
~~~~~~~~~~~~~~~~~
idle machine at 1.7GHz, min bl: 13.0 W
idle machine at 600MHz, min bl: 12.0 W

thinkpad x32 [52Wh]
~~~~~~~~~~~~
idle machine at 600MHz, min bl:         10 W
             at 1.8GHz:                 +6.6 W

hp nx5k [56.8Wh]
~~~~~~~
idle, min bl:                   19 W
      min bl, 1.4GHz:           22 W

...so yes, I kind of see a pattern there. And you should be able to
easily see the difference, too, if you took something from that era...

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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