[PATCH] Dynamic sched domains: sched changes

The following patches add dynamic sched domains functionality that was
extensively discussed on lkml and lse-tech.  I would like to see this added to
-mm

o The main advantage with this feature is that it ensures that the scheduler
  load balacing code only balances against the cpus that are in the sched
  domain as defined by an exclusive cpuset and not all of the cpus in the
  system. This removes any overhead due to load balancing code trying to
  pull tasks outside of the cpu exclusive cpuset only to be prevented by
  the tasks' cpus_allowed mask.
o cpu exclusive cpusets are useful for servers running orthogonal
  workloads such as RT applications requiring low latency and HPC
  applications that are throughput sensitive

o It provides a new API partition_sched_domains in sched.c
  that makes dynamic sched domains possible.
o cpu_exclusive cpusets sets are now associated with a sched domain.
  Which means that the users can dynamically modify the sched domains
  through the cpuset file system interface
o ia64 sched domain code has been updated to support this feature as well
o Currently, this does not support hotplug. (However some of my tests
  indicate hotplug+preempt is currently broken)
o I have tested it extensively on x86.
o This should have very minimal impact on performance as none of
  the fast paths are affected

Signed-off-by: Dinakar Guniguntala <dino@in.ibm.com>
Acked-by: Paul Jackson <pj@sgi.com>
Acked-by: Nick Piggin <nickpiggin@yahoo.com.au>
Acked-by: Matthew Dobson <colpatch@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>