sched/numa: Use effective_load() to balance NUMA loads

sched/numa: Use effective_load() to balance NUMA loads

When CONFIG_FAIR_GROUP_SCHED is enabled, the load that a task places
on a CPU is determined by the group the task is in. The active groups
on the source and destination CPU can be different, resulting in a
different load contribution by the same task at its source and at its
destination. As a result, the load needs to be calculated separately
for each CPU, instead of estimated once with task_h_load().

Getting this calculation right allows some workloads to converge,
where previously the last thread could get stuck on another node,
without being able to migrate to its final destination.

Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: mgorman@suse.de
Cc: chegu_vinod@hp.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1403538378-31571-3-git-send-email-riel@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>