Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Scheduling module to introduce a fixed delay into the I/O path.

Bring in geom_sched, support for scheduling disk I/O requests
in a device independent manner. Also include an example anticipatory
scheduler, gsched_rr, which gives very nice performance improvements
in presence of competing random access patterns.

This is joint work with Fabio Checconi, developed last year
and presented at BSDCan 2009. You can find details in the
README file or at

http://info.iet.unipi.it/~luigi/geom_sched/