Fighting for the power.

Alexander Motin mav at
Mon May 11 23:13:39 UTC 2009

Paul B. Mahol wrote:
> On 5/11/09, Alexander Motin <mav at> wrote:
>> Tim Kientzle wrote:
>>> I started to try the "hint.apic.0.clock", but noticed
>>> in your commit r191720:
>>> Alexander Motin wrote:
>>>> Add hint.apic.0.clock tunable. Setting it 0 disables using
>>>> LAPIC timers as hard-/stat-/profclock sources falling back
>>>> to using i8254 and rtc timers.
>>>> ...
>>>> This technique is not working for SMP yet, as only one CPU
>>>> receives timer interrupts. But I think that problem could
>>>> be fixed by forwarding interrupts to other CPUs with IPI.
>>> Is anyone looking at this yet?
>> I have implemented SMP support for i386 and amd64 in some of my later
>> commits.
> And all those hacks helps verry little in my case, most gain I get when
> laptop monitor is switched off. Even switching hard disk off improves battery
> life very little.

Monitor is surely one of major power consumers, but there are not so 
much things which you can do about it, as without power there will be no 
  backlight. All you can do is tune backlight to minimum level required 
in every specific situation.

What's about general effect, the main idea here is the same as in audio 
processing: result mostly depends on quality of the worst component. 
Your system may just have some other consumers which I don't have. For 
example, desktop CPU instead of mobile, desktop chipset instead of 
mobile, powerful external video instead of (or even in addition to) 
built-in, and so on.

Alexander Motin

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