Saving the world one uW at a time

I'm here at UDS and joined a session between the kernel and desktop teams talking about power. Like all of such sessions the kernel team thinks that the desktop should fix all the problems and vice versa. At their suggestion, I took an action item.

One of the features of GTK+ is that it provides two timeout functions: gtk_timeout_add and gtk_timeout_add_seconds. The difference is much more important than not having to add a "* 1000" in one and not the other. The important thing that the second function does is that it tried to group wake-ups to ensure that the program wakes up as little as possible. This is never perfect, but it's a small thing that can help to save some power and reduce the number of wake-ups.

So I looked through the Ubuntu main archive to figure out how many applications use the more precise function, but just pass in several seconds as the parameter. I figured this would be a few apps, and I'd submit a couple patches, then I could go back to blaming the kernel team for all our problems. There are more than a couple packages. There are a lot of packages. The results of the grep and a cleaned up list of packages that are likely to have easy fixes.

I realize now that I can't do this by myself, the only hope is to document how to fix it.

So if you'd like to help save a little power on your machine, follow these instructions.

  1. Take one of the packages in the list above and find it in the package repository (instructions).
  2. Branch it:
    $ bzr branch http://package-import.ubuntu.com/x/xproject/jaunty localfix
  3. Find the instances that might be causing the problem.
    $ rgrep timeout_add *
  4. Commit and build a package:
    $ bzr commit -m "Saving the world"
    $ dch -i
    $ debuild
  5. Test it on your system, make sure things still work reasonably.
  6. Generate a patch:
    $ bzr diff -r ancestor:
  7. Submit it upstream!

posted on Wed, 10 Dec 2008 at 15:28 | permanent link