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Date:      Fri, 27 Oct 2006 09:35:48 -0700
From:      Sam Leffler <sam@errno.com>
To:        Nate Lawson <nate@root.org>
Cc:        acpi@freebsd.org
Subject:   Re: powerd: add support for limiting cpu frequency on adaptive mode
Message-ID:  <45423564.8030703@errno.com>
In-Reply-To: <45422F17.4000704@root.org>
References:  <Pine.BSF.3.96.1061027175636.1051A-100000@gaia.nimnet.asn.au> <45422F17.4000704@root.org>

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Nate Lawson wrote:
> Ian Smith wrote:
>> On Thu, 26 Oct 2006, Kevin Oberman wrote:
>>
>>  > > Can someone look on the pr
>>  > > (http://www.freebsd.org/cgi/query-pr.cgi?pr=bin/104689) I sent.
>> Maybe
>>  > > the patch is dirty but I think that idea is nice and with it battery
>>  > > lives really longer.
>>  >  > YES! When I am on battery for an extended time, I am very happy
>> to have
>>  > the system max out at a MUCH lower speed if I can keep basic
>> capabilities
>>  > for simple stuff like editing and such. Slight slow-downs are not an
>>  > issue.
>>
>> The problem I see with this patch as it stands is that it affects both
>> battery and AC power adaptive modes (ie, powerd default operating mode)
>>
>> Stepan says in the PR:
>>
>>  "Apply the patch and run powerd:
>>  powerd -a maximum -b adaptive -m 558
>>  Where 558 is maximum frequency on adaptive mode"
>>
>> I want to run adaptive mode on 'AC' both because it uses half the power
>> when idle and greatly reduces the laptop's temperature (Thinkpad T23).
>> 'AC' in quotes, this being a 100% solar power home; every watt counts.
>> Were the -m switch function ANDed with (acline_status = SRC_BATTERY) or
>> perhaps, allowing for SRC_UNKNOWN, (acline_status != SRC_AC) then you
>> could still use adaptive mode at full speed on 'AC' when required and
>> take advantage of setting a maximum speed while running on battery?
>>  > That said, power consumption is NOT intuitive. If I am playing an MP3
>>  > (very constant CPU load) at  a speed where the CPU is at about 80%,
>> the
>>  > system uses more power than when the CPU is at 30%. In either case,
>> the
>>  > MP3 playback is fine. (This was on my T30 with a 1.8G P4M CPU, so it's
>>  > not the best for power use.)
>>
>> The T23 is only a two-speed P3M (1133/733) so I've yet to see the full
>> potential of powerd, nor have I played with its idle/busy shift points
>> or examined hysteresis between load shift points at various freqs, but
>> it's already a Very Good Thing here ..
>>
>>  > I know that Windows wants to reduce maximum CPU speed when running on
>>  > battery, so I do believe this is a good thing.
>>
>> If limited to while running on battery only, I'd heartily agree.
>> Meanwhile of course you can run powerd -b min though that might be
>> overkill if you have lots of freqs available .. 
> 
> I'll say it again:  we need real profiles, not more command line flags.
>  The first person to add a .y and define a config file format gets a
> cookie.  I just haven't found anyone willing to put in that design effort.
> 

Config files are great but I think something more dynamic is needed.  In
particular I'd like to see devd launch tools that inform powerd it
should switch operating mode from AC -> battery.  Otherwise powerd needs
this builtin and then we'll have no good place to centralize
power-related work (e.g. like setting wireless cards into power save
mode when operating in sta mode and on battery).  Or perhaps I'm not
clueful here...

	Sam




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