sched, nohz: Introduce nohz_flags in 'struct rq'

Introduce nohz_flags in the struct rq, which will track these two flags
for now.

NOHZ_TICK_STOPPED keeps track of the tick stopped status that gets set when
the tick is stopped. It will be used to update the nohz idle load balancer data
structures during the first busy tick after the tick is restarted. At this
first busy tick after tickless idle, NOHZ_TICK_STOPPED flag will be reset.
This will minimize the nohz idle load balancer status updates that currently
happen for every tickless exit, making it more scalable when there
are many logical cpu's that enter and exit idle often.

NOHZ_BALANCE_KICK will track the need for nohz idle load balance
on this rq. This will replace the nohz_balance_kick in the rq, which was
not being updated atomically.

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/20111202010832.499438999@sbsiddha-desk.sc.intel.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 10 insertions, 1 deletions

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 8715055979d1..cf7d02662bc2 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -371,7 +371,7 @@ struct rq {
         unsigned long last_load_update_tick;
 #ifdef CONFIG_NO_HZ
         u64 nohz_stamp;
-        unsigned char nohz_balance_kick;
+        unsigned long nohz_flags;
 #endif
         int skip_clock_update;
 
@@ -1064,3 +1064,12 @@ extern void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq);
 extern void unthrottle_offline_cfs_rqs(struct rq *rq);
 
 extern void account_cfs_bandwidth_used(int enabled, int was_enabled);
+
+#ifdef CONFIG_NO_HZ
+enum rq_nohz_flag_bits {
+        NOHZ_TICK_STOPPED,
+        NOHZ_BALANCE_KICK,
+};
+
+#define nohz_flags(cpu) (&cpu_rq(cpu)->nohz_flags)
+#endif