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Date: Mon, 17 Mar 2008 21:18:36 +0100
From: Kris Kennaway <kris@FreeBSD.org>
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To: Poul-Henning Kamp <phk@phk.freebsd.dk>
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Cc: arch@freebsd.org
Subject: Re: Power-Mgt (Was: Re: cvs commit: src/sys/i386/cpufreq est.c )
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Poul-Henning Kamp wrote:
> In message <20080317141717.U3253@fledge.watson.org>, Robert Watson writes:
> 
>> If cpufreq is going to be enabled by default, should we be enabling powerd by 
>> default [...]
> 
> [Moved to arch@]
> 
> In general, I think we must make power-aware computing our "next
> SMPng project", not in the sense of delaying the next major release
> five years, but in the sense that power consumption should permerate
> our thinking about the operating system from now on.
> 
> Overall, I think that means that we should:
> 
> *  Enable performance neutral power savings on servers
> 	- spin down unused disks. (geom/drivers)
> 	- use only as many CPU cores as necessary (scheduler)
> 	- light cpu-throttling.
> 	- downgrading 1GB to 100MB ether when idle.
> 
> *  Aim to meet or execeed energystar 4.0/5.0[1] on desktops and 
>    plugged laptops.
> 	- Pretty much as above, but with specific targets.
> 	- http://www.energystar.gov/index.cfm?c=revisions.computer_spec
> 
> *  Be as battery-frugal as possible on battery driven laptops.
> 	- Any trick in and off the book.

I think this is a great idea, but one of the big problems is probably 
going to be dealing with hardware quirks.  e.g. we can't even enable 
powerd by default because e.g. acpi_throttle hangs on some systems.  It 
might be tricky to get power management to the stage where it works for 
everyone and can be done automatically.

Kris