linux-kernel - Re: RFC: A proposal for power capping through forced idle in the Linux Kernel

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20091223094905.GC24181@elf.ucw.cz>
Date:	Wed, 23 Dec 2009 10:49:05 +0100
From:	Pavel Machek <pavel@....cz>
To:	Salman Qazi <sqazi@...gle.com>
Cc:	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Michael Rubin <mrubin@...gle.com>,
	Taliver Heath <taliver@...gle.com>
Subject: Re: RFC: A proposal for power capping through forced idle in the
 Linux Kernel

On Tue 2009-12-22 13:10:36, Salman Qazi wrote:
> On Fri, Dec 18, 2009 at 9:04 AM, Pavel Machek <pavel@....cz> wrote:
> > Hi
> >
> >
> >> Why not use voltage and frequency scaling?
> >>
> >> Forced Idle Injection is more effective[1] and more widely available.
> >> Even with voltage and frequency scaling, interpolation is needed
> >> between the available settings.  So, if we did use voltage and
> >
> > It is only more efficient on new hardware.
> >
> > You should also explain 'why not throttling' because that is actually
> > designed for power capping.
> 
> Do you mean t-states?

Yes.

> >> Application to Laptops and Cellphones:
> >>
> >> Imagine being in a tent in Death Valley with a laptop.  You are bored,
> >> and you want to watch a movie.  However, you also want to do your best
> >> to make the battery last and watch as much of the movie as possible.
> >> Forced idle power capping is a solution.  If your machine has a knob
> >> that allows you to control the available power, you can turn that knob
> >> until your video starts getting choppy.  And then, turn the knob back
> >
> > That's bad example. Video player should already sleep between frames.
> 
> Yes, the video player should sleep.  However, there will be other
> things running.  And certainly, it is possible to cap the power and
> discriminate so that those things are prevented from running while the
> video player is allowed to run with minimal latency impact.

I don't see how it would work without much of extra setup. Lets say
your windowmanager wants to do some work, and you starve it
indefinitely?
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/