"With all the tickless [story] and other goodies going into the kernel in the last few months, there is a lot of hope that this helps Linux reduce power consumption," Arjan van de Ven began on the lkml, "and the good news is that it does... once you fix some bugs and fix a bunch of userspace applications." He referred to a promising graph generated utilizing the recently introduced PowerTOP utility [story], measuring power consumption before and after applying a series of related bug fixes.

The tests began with a Lenovo T61 laptop running the stock 32-bit Fedora 7 kernel which includes the tickless kernel. This was compared against the stock 2.6.22-rc4 kernel with a series of improvements including a fix for the Ondemand CPUFREQ governor, the new CPUIDLE infrastructure, the Active Link Power Management patch, disabling the laptop's TV-out capability, and using a cli utility to properly reduce the laptop's backlight. Arjan summarizes, "with kernel fixes and features, the power consumption of this laptop went from 21.06 Watts to 18.25 Watts; with 2 additional userspace fixes the power consumption ended up at 15.5 Watts."

From:	Arjan van de Ven [email blocked]
To: 	linux-kernel
Subject: Liunx power consumption on laptops -- Enormous progress in the last few months
Date:	Thu, 05 Jul 2007 12:58:58 -0700

Hi,

with all the tickless and other goodies going into the kernel in the 
last few months, there is a lot of hope that this helps Linux reduce 
power consumption... and the good news is that it does... once you fix 
some bugs and fix a bunch of userspace applications.

While it's hard to show "one size fits all" number/percentage, we took 
a bog standard Lenovo T61 laptop (no vendor preference, they just were 
the first one to deliver a model with the latest Intel chipset to our 
cubes) and measured the effect. The baseline we used was a 32 bit 
Fedora 7 installation; note that this already has the tickless kernel, 
but is lacking several of the key bugfixes that came afterwards.

We've put our measurements in a graph at

http://www.linuxpowertop.org/results.php

With kernel fixes and features, the power consumption of this laptop 
went from 21.06 Watts to 18.25 Watts; with 2 additional userspace 
fixes the power consumption ended up at 15.5 Watts.

(Don't worry that this is the end of it; there's more stuff in the 
various project pipelines, and we'll keep measuring the progress over 
time)


All in all, personally I'm very happy to see Linux making such a huge 
step forward with tickless and can't wait for this step to be 
available in all distros and for all architectures...

Greetings,
    Arjan van de Ven

• Archive of above thread