From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dominik Brodowski <linux@dominikbrodowski.net>
Subject: Re: Status of X86_P4_CLOCKMOD?
Date: Tue, 28 Feb 2006 22:34:28 +0100
Message-ID: <20060228213428.GA31044@isilmar.linta.de>
References: <20060222024438.GI20204@MAIL.13thfloor.at> <20060222031001.GC4661@stusta.de> <200602212220.05642.dtor_core@ameritech.net> <20060223195937.GA5087@stusta.de> <20060223204110.GE6213@redhat.com> <20060228194628.GP4650@waste.org> <20060228200916.GA326@redhat.com> <20060228204720.GD13116@waste.org> <20060228205758.GA16268@isilmar.linta.de> <20060228212632.GE13116@waste.org>
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To: Matt Mackall <mpm@selenic.com>
Cc: Dave Jones <davej@redhat.com>, Adrian Bunk <bunk@stusta.de>, Dmitry Torokhov <dtor_core@ameritech.net>, davej@codemonkey.org.uk, Zwane Mwaikambo <zwane@commfireservices.com>, Samuel Masham <samuel.masham@gmail.com>, Jan Engelhardt <jengelh@linux01.gwdg.de>, linux-kernel@vger.kernel.org, Andrew Morton <akpm@osdl.org>, cpufreq@lists.linux.org.uk, ak@suse.de

On Tue, Feb 28, 2006 at 03:26:32PM -0600, Matt Mackall wrote:
> > So even if the battery lasts longer, you don't have anything of it,=
 'cause
> > the CPU can even compute _less_ in this longer time-span. Remember =
that
> > idling doesn't count...
>=20
> Which is different from other power-saving modes how? If it means I
> can read my email longer on the plane, it's a power-saving mode.

But you can't... [*]

> > > In short, power usage and heat production are _the same thing_.
> >=20
> > Yes and no. The heat production is more levelled if you use throttl=
ing, so
> > the temperature achieved is lesser, which might cause fans not havi=
ng to
> > start or air conditioning having less work to do.
>=20
> The time scale for heat propagation is enough slower than throttling
> that I'd expect this difference to amount to approximately nil.

=46or short-term load spikes, yes. If your server has a task which take=
s up
one hour at full time, and the temp reaches 45=B0 C then, but you have =
nothing
else for it to do overnight, then it does might sense to throttle it to
50%, which will mean two hours, but only 40=B0 C.

	Dominik


[*] unless the idling algorithm is broken and does not enter C2-type id=
le
states.