[RFC PATCH v2 7/8] cpuidle: introduce irq timing to make idle prediction

Aubrey Li
2017-09-30T07:21:51Z

Introduce irq timings output as a factor to predict the duration
of the coming idle

Signed-off-by: Aubrey Li <aubrey.li@linux.intel.com>
---
drivers/cpuidle/Kconfig | 1 +
drivers/cpuidle/cpuidle.c | 17 ++++++++++++++++-
2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/cpuidle/Kconfig b/drivers/cpuidle/Kconfig
index 7e48eb5..8b07e1c 100644
--- a/drivers/cpuidle/Kconfig
+++ b/drivers/cpuidle/Kconfig
@@ -5,6 +5,7 @@ config CPU_IDLE
default y if ACPI || PPC_PSERIES
select CPU_IDLE_GOV_LADDER if (!NO_HZ && !NO_HZ_IDLE)
select CPU_IDLE_GOV_MENU if (NO_HZ || NO_HZ_IDLE)
+ select IRQ_TIMINGS
help
CPU idle is a generic framework for supporting software-controlled
idle processor power management. It includes modular cross-platform
diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c
index 5d4f0b6..be56cea 100644
--- a/drivers/cpuidle/cpuidle.c
+++ b/drivers/cpuidle/cpuidle.c
@@ -22,6 +22,7 @@
#include <linux/module.h>
#include <linux/suspend.h>
#include <linux/tick.h>
+#include <linux/interrupt.h>
#include <trace/events/power.h>

#include "cpuidle.h"
@@ -342,13 +343,27 @@ void cpuidle_entry_end(void)
void cpuidle_predict(void)
{
struct cpuidle_device *dev = cpuidle_get_device();
- unsigned int overhead_threshold;
+ unsigned int idle_interval, overhead_threshold;
+ u64 now, next_evt;

if (!dev)
return;

overhead_threshold = dev->idle_stat.overhead * sysctl_fast_idle_ratio;

+ /*
+ * check irq timings if the next event is coming soon
+ */
+ now = local_clock();
+ local_irq_disable();
+ next_evt = irq_timings_next_event(now);
+ local_irq_enable();
+ idle_interval = div_u64(next_evt - now, NSEC_PER_USEC);
+ if (idle_interval < overhead_threshold) {
+ dev->idle_stat.fast_idle = true;
+ return;
+ }
+
if (cpuidle_curr_governor->predict) {
dev->idle_stat.predicted_us = cpuidle_curr_governor->predict();
/*
--
2.7.4