linux-kernel - [RFC PATCH v2 2/2] power/idle: enhance the precision of sleep

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Message-ID: <57591c5e.582b620a.f8dc2.19dd@mx.google.com>
Date:	Thu,  9 Jun 2016 15:34:44 +0800
From:	zhaoyang.huang@...aro.org
To:	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	mingo@...hat.com, peterz@...radead.org,
	zhaoyang.huang@...eadtrum.com, tglx@...utronix.de
Subject: [RFC PATCH v2 2/2] power/idle: enhance the precision of sleep_length

From: Zhaoyang Huang <zhaoyang.huang@...eadtrum.com>

There should be a gap between tick_nohz_idle_enter and
tick_nohz_get_sleep_length when idle, which will cause the
sleep_length is not very precised. Change it in this patch.

Signed-off-by: Zhaoyang Huang <zhaoyang.huang@...eadtrum.com>
---
 kernel/time/tick-sched.c |    5 +++++
 1 file changed, 5 insertions(+)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 536ada8..ee3be3d 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -975,6 +975,11 @@ void tick_nohz_irq_exit(void)
 ktime_t tick_nohz_get_sleep_length(void)
 {
 	struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
+	struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
+	ktime_t now;
+
+	now = ktime_get();
+	ts->sleep_length = ktime_sub(dev->next_event, now);
 
 	return ts->sleep_length;
 }
-- 
1.7.9.5