Sucking power

Posted Sep 13, 2007 3:12 UTC (Thu) by JoeBuck (subscriber, #2330) [Link]

My guess is that some of what we consider userspace, they consider part of the OS (specifically, all those cool KDE and Gnome features). I think Windows has paid a cost for the tighter integration (more security issues) but might also have seen some benefits in the power area.

Posted Sep 13, 2007 16:04 UTC (Thu) by iabervon (subscriber, #722) [Link]

My feeling is that a smaller portion of applications on Windows do anything at all when they aren't the user's main task. There's a relatively small set of applications that will interrupt you (many of which are integrated with the kernel and sleep on input from drivers instead of polling), and some that play background music, but mostly they don't do anything when they don't have focus. Linux doesn't have so much of a mechanism for telling applications whether the user cares about them (and tends to have users watching a dozen things out of the corners of their eyes), so everything has to be polling if the things it is supposed to respond to aren't things that can be blocked on.

It's also the case with Gtk+ at least that it's hard to get good results out of multiple threads (each of which blocks on a different input) all updating the display; the only easy thing that works (last time I checked) is to have a single thread poll for input having happened and take care of responding. I think Windows has a totally different locking model that requires less polling.

Of course, I run a particularly old-school UI on my laptop, and I've been getting ~14 W for interaction stuff (i.e., when I'm not actually creating significant load; how much power doing work uses is a separate issue). On my laptop, the main sources of wakeups seem to be that the trackpad's input doesn't get batched at all and is high-frequency when in use, and iwlwifi is always busy.

Posted Sep 16, 2007 3:36 UTC (Sun) by sobdk (guest, #38278) [Link]

What makes you think Windows doesn't have a similar problem? With all of the crap you have to install on Windows like virus scanners, anti-spyware tools, internet security suites I'm sure the situation is much much worse. You did get me curious enough to do a little test today on my wife's machine that has both Windows Vista (pretty much a bare install with virus software) and Kubuntu.

The awesome power of Windows Vista!

The gist is that on the same machine Windows would idle at about 79 Watts but Kubuntu 7.04 with a kernel.org 2.6.22.6 used 69 Watts. The real kicker for me was that even though I thought we had been putting the machine to sleep in Windows all of this time it actually does nothing!