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Subject[PATCH 4/4] sched: Conditionally build cpu load decay code for nohz
Date
To complete the tick periodic kernel optimizations.

Cc: Byungchul Park <byungchul.park@lge.com>
Cc: Chris Metcalf <cmetcalf@ezchip.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Luiz Capitulino <lcapitulino@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
---
kernel/sched/fair.c | 41 ++++++++++++++++++++++++++++++-----------
1 file changed, 30 insertions(+), 11 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1bb053e..0bb872e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4423,6 +4423,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
}

#ifdef CONFIG_SMP
+#ifdef CONFIG_NO_HZ_COMMON

/*
* per rq 'load' arrray crap; XXX kill this.
@@ -4490,6 +4491,33 @@ decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
return load;
}

+static unsigned long
+cpu_load_update_missed(unsigned long old_load, unsigned long tickless_load,
+ unsigned long pending_updates, int idx)
+{
+ old_load = decay_load_missed(old_load, pending_updates - 1, idx);
+ if (tickless_load) {
+ old_load -= decay_load_missed(tickless_load, pending_updates - 1, idx);
+ /*
+ * old_load can never be a negative value because a
+ * decayed tickless_load cannot be greater than the
+ * original tickless_load.
+ */
+ old_load += tickless_load;
+ }
+ return old_load;
+}
+#else /* !CONFIG_NO_HZ_COMMON */
+
+static inline unsigned long
+cpu_load_update_missed(unsigned long old_load, unsigned long tickless_load,
+ unsigned long pending_updates, int idx)
+{
+ return old_load;
+}
+
+#endif /* CONFIG_NO_HZ_COMMON */
+
/**
* __cpu_load_update - update the rq->cpu_load[] statistics
* @this_rq: The rq to update statistics for
@@ -4541,17 +4569,8 @@ static void cpu_load_update(struct rq *this_rq, unsigned long this_load,

/* scale is effectively 1 << i now, and >> i divides by scale */

- old_load = this_rq->cpu_load[i];
- old_load = decay_load_missed(old_load, pending_updates - 1, i);
- if (tickless_load) {
- old_load -= decay_load_missed(tickless_load, pending_updates - 1, i);
- /*
- * old_load can never be a negative value because a
- * decayed tickless_load cannot be greater than the
- * original tickless_load.
- */
- old_load += tickless_load;
- }
+ old_load = cpu_load_update_missed(this_rq->cpu_load[i],
+ tickless_load, pending_updates, i);
new_load = this_load;
/*
* Round up the averaging division if load is increasing. This
--
2.7.0
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