Re: Tree based scheduling

Jeremy Fitzhardinge (
Sun, 18 Jan 1998 02:35:39 +1100

Rauli Ruohonen wrote:
> I wrote this little document a while ago but never got around coding the
> thing.. I might give it a shot when I have more time, but before I do
> anything: Comments? Is this a good idea? Note that I don't know the kernel
> code very well and probably can't code this yet, so don't expect
> anything.. :)

Have a look at ShareII at It's a commercial product
which contains a user-oriented heirachical scheduler like this. It
works well, but it's complex to get a reasonable "fairness" between
users. One specifies the share each user gets with respect to their
peers, and the scheduler tries to enforce it, using historical
information to deal with a user who saturates the CPU(s) on an idle
machine who later competes with users on a busy machine.

User scheduling is not only useful for real users - its a great way of
making sure daemons get the amount of CPU they need without saturating
the machine if they run wild.

Bias warning: I work at Softway, often on Share.