[RFC][PATCH 3/3] cpuidle,teo: Improve state selection

[Peter Zijlstra]

When selecting a state, stop when history tells us 66% of recent idles
were at or below our current state.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
 drivers/cpuidle/governors/teo.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/drivers/cpuidle/governors/teo.c
+++ b/drivers/cpuidle/governors/teo.c
@@ -363,6 +363,7 @@ static int teo_select(struct cpuidle_dri
 	unsigned int idx_hit_sum = 0;
 	unsigned int hit_sum = 0;
 	unsigned int tick_sum = 0;
+	unsigned int thresh_sum = 0;
 	int constraint_idx = 0;
 	int idx0 = 0, idx = -1;
 	bool alt_intercepts, alt_recent;
@@ -397,6 +398,8 @@ static int teo_select(struct cpuidle_dri
 		duration_ns = tick_nohz_get_sleep_length(&delta_tick);
 	cpu_data->sleep_length_ns = duration_ns;
 
+	thresh_sum = 2 * cpu_data->total / 3; /* 66% */
+
 	/*
 	 * Find the deepest idle state whose target residency does not exceed
 	 * the current sleep length and the deepest idle state not deeper than
@@ -427,6 +430,9 @@ static int teo_select(struct cpuidle_dri
 		if (s->target_residency_ns > duration_ns)
 			break;
 
+		if (intercept_sum + hit_sum > thresh_sum)
+			break;
+
 		idx = i;
 
 		if (s->exit_latency_ns <= latency_req)