where are graph algorithms used under an operating system project?

[Mayuresh Kathe <mayuresh%sdf.org@localhost>]

due to a lack of background in formal computer science, i was under the
impression that graph algorithms are only useful in networking related
applications/areas. just noticed that even scheduling requires some level
of graph algorithm knowledge. am i right in my reading/observation? if not
which areas of an operating system require a good grasp of graph algorithms?
thank you.