[RFC PATCH v2 6/8] cpuidle: make fast idle threshold tunable

[Aubrey Li <aubrey.li@intel.com>]

Add a knob to make fast idle threshold tunable

Signed-off-by: Aubrey Li <aubrey.li@linux.intel.com>
---
 drivers/cpuidle/cpuidle.c |  3 ++-
 include/linux/cpuidle.h   |  1 +
 kernel/sysctl.c           | 12 ++++++++++++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 6cb7e17..5d4f0b6 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -35,6 +35,7 @@ LIST_HEAD(cpuidle_detected_devices);
 static int enabled_devices;
 static int off __read_mostly;
 static int initialized __read_mostly;
+int sysctl_fast_idle_ratio = 10;
 
 int cpuidle_disabled(void)
 {
@@ -346,7 +347,7 @@ void cpuidle_predict(void)
 	if (!dev)
 		return;
 
-	overhead_threshold = dev->idle_stat.overhead;
+	overhead_threshold = dev->idle_stat.overhead * sysctl_fast_idle_ratio;
 
 	if (cpuidle_curr_governor->predict) {
 		dev->idle_stat.predicted_us = cpuidle_curr_governor->predict();
diff --git a/include/linux/cpuidle.h b/include/linux/cpuidle.h
index 791db15..45b8264 100644
--- a/include/linux/cpuidle.h
+++ b/include/linux/cpuidle.h
@@ -24,6 +24,7 @@ struct module;
 struct cpuidle_device;
 struct cpuidle_driver;
 
+extern int sysctl_fast_idle_ratio;
 
 /****************************
  * CPUIDLE DEVICE INTERFACE *
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 6648fbb..97f7e8af 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -67,6 +67,7 @@
 #include <linux/kexec.h>
 #include <linux/bpf.h>
 #include <linux/mount.h>
+#include <linux/cpuidle.h>
 
 #include <linux/uaccess.h>
 #include <asm/processor.h>
@@ -1229,6 +1230,17 @@ static struct ctl_table kern_table[] = {
 		.extra2		= &one,
 	},
 #endif
+#ifdef CONFIG_CPU_IDLE
+	{
+		.procname       = "fast_idle_ratio",
+		.data           = &sysctl_fast_idle_ratio,
+		.maxlen         = sizeof(int),
+		.mode           = 0644,
+		.proc_handler   = proc_dointvec_minmax,
+		.extra1         = &one,
+		.extra2         = &one_hundred,
+	},
+#endif
 	{ }
 };
 
-- 
2.7.4