sched, nohz: Track nr_busy_cpus in the sched_group_power

Introduce nr_busy_cpus in the struct sched_group_power [Not in sched_group
because sched groups are duplicated for the SD_OVERLAP scheduler domain]
and for each cpu that enters and exits idle, this parameter will
be updated in each scheduler group of the scheduler domain that this cpu
belongs to.

To avoid the frequent update of this state as the cpu enters
and exits idle, the update of the stat during idle exit is
delayed to the first timer tick that happens after the cpu becomes busy.
This is done using NOHZ_IDLE flag in the struct rq's nohz_flags.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20111202010832.555984323@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 1 insertions, 0 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 7f1da77b83f3..699ff1499a8a 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6024,6 +6024,7 @@ static void init_sched_groups_power(int cpu, struct sched_domain *sd)
                 return;
 
         update_group_power(sd, cpu);
+        atomic_set(&sg->sgp->nr_busy_cpus, sg->group_weight);
 }
 
 int __weak arch_sd_sibling_asym_packing(void)