[RFC PATCH v1 04/11] sched/idle: make the fast idle path for short idle periods

Aubrey Li
2017-07-10T01:49:02Z

From: Aubrey Li <aubrey.li@linux.intel.com>

The system will enter a fast idle loop if the predicted idle period
is shorter than the threshold.
---
kernel/sched/idle.c | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c
index cf6c11f..16a766c 100644
--- a/kernel/sched/idle.c
+++ b/kernel/sched/idle.c
@@ -280,6 +280,8 @@ static void cpuidle_generic(void)
*/
static void do_idle(void)
{
+ unsigned int predicted_idle_us;
+ unsigned int short_idle_threshold = jiffies_to_usecs(1) / 2;
/*
* If the arch has a polling bit, we maintain an invariant:
*
@@ -291,7 +293,12 @@ static void do_idle(void)

__current_set_polling();

- cpuidle_generic();
+ predicted_idle_us = cpuidle_predict();
+
+ if (likely(predicted_idle_us < short_idle_threshold))
+ cpuidle_fast();
+ else
+ cpuidle_generic();

__current_clr_polling();

--
2.7.4