more sched_clock updates

Index: linux-tip.git/kernel/sched_clock.c
===================================================================
@@ -124,7 +124,7 @@ static int check_max(struct sched_clock_
  *  - filter out backward motion
  *  - use jiffies to generate a min,max window to clip the raw values
  */
-static void __update_sched_clock(struct sched_clock_data *scd, u64 now)
+static void __update_sched_clock(struct sched_clock_data *scd, u64 now, u64 *time)
 {
 	unsigned long now_jiffies = jiffies;
 	long delta_jiffies = now_jiffies - scd->tick_jiffies;

@@ -162,8 +162,12 @@ static void __update_sched_clock(struct 
 	if (unlikely(clock < min_clock))
 		clock = min_clock;
 
-	scd->prev_raw = now;
-	scd->clock = clock;
+	if (time)
+		*time = clock;
+	else {
+		scd->prev_raw = now;
+		scd->clock = clock;
+	}
 }
 
 static void lock_double_clock(struct sched_clock_data *data1,

@@ -207,15 +211,18 @@ u64 sched_clock_cpu(int cpu)
 		now -= scd->tick_gtod;
 
 		__raw_spin_unlock(&my_scd->lock);
+
+		__update_sched_clock(scd, now, &clock);
+
+		__raw_spin_unlock(&scd->lock);
+
 	} else {
 		__raw_spin_lock(&scd->lock);
+		__update_sched_clock(scd, now, NULL);
+		clock = scd->clock;
+		__raw_spin_unlock(&scd->lock);
 	}
 
-	__update_sched_clock(scd, now);
-	clock = scd->clock;
-
-	__raw_spin_unlock(&scd->lock);
-
 	return clock;
 }
 

@@ -234,7 +241,7 @@ void sched_clock_tick(void)
 	now_gtod = ktime_to_ns(ktime_get());
 
 	__raw_spin_lock(&scd->lock);
-	__update_sched_clock(scd, now);
+	__update_sched_clock(scd, now, NULL);
 	/*
 	 * update tick_gtod after __update_sched_clock() because that will
 	 * already observe 1 new jiffy; adding a new tick_gtod to that would

Index: linux-tip.git/kernel/sched_clock.c
===================================================================
@@ -237,8 +237,8 @@ void sched_clock_tick(void)
 
 	WARN_ON_ONCE(!irqs_disabled());
 
-	now = sched_clock();
 	now_gtod = ktime_to_ns(ktime_get());
+	now = sched_clock();
 
 	__raw_spin_lock(&scd->lock);
 	__update_sched_clock(scd, now, NULL);

Index: linux-tip.git/kernel/sched_clock.c
===================================================================
@@ -3,6 +3,9 @@
  *
  *  Copyright (C) 2008 Red Hat, Inc., Peter Zijlstra <[email protected]>
  *
+ *  Updates and enhancements:
+ *    Copyright (C) 2008 Red Hat, Inc. Steven Rostedt <[email protected]>
+ *
  * Based on code by:
  *   Ingo Molnar <[email protected]>
  *   Guillaume Chazarain <[email protected]>

@@ -32,6 +35,11 @@
 
 #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
 
+#define MULTI_SHIFT 15
+/* Max is double, Min is 1/2 */
+#define MAX_MULTI (2LL << MULTI_SHIFT)
+#define MIN_MULTI (1LL << (MULTI_SHIFT-1))
+
 struct sched_clock_data {
 	/*
 	 * Raw spinlock - this is a special case: this might be called

@@ -45,6 +53,7 @@ struct sched_clock_data {
 	u64			tick_raw;
 	u64			tick_gtod;
 	u64			clock;
+	s64			multi;
 #ifdef CONFIG_NO_HZ
 	int			check_max;
 #endif

@@ -79,6 +88,7 @@ void sched_clock_init(void)
 		scd->tick_raw = 0;
 		scd->tick_gtod = ktime_now;
 		scd->clock = ktime_now;
+		scd->multi = 1 << MULTI_SHIFT;
 #ifdef CONFIG_NO_HZ
 		scd->check_max = 1;
 #endif

@@ -134,8 +144,13 @@ static void __update_sched_clock(struct 
 
 	WARN_ON_ONCE(!irqs_disabled());
 
-	min_clock = scd->tick_gtod +
-		(delta_jiffies ? delta_jiffies - 1 : 0) * TICK_NSEC;
+	/*
+	 * At schedule tick the clock can be just under the gtod. We don't
+	 * want to push it too prematurely.
+	 */
+	min_clock = scd->tick_gtod + (delta_jiffies * TICK_NSEC);
+	if (min_clock > TICK_NSEC)
+		min_clock -= TICK_NSEC / 2;
 
 	if (unlikely(delta < 0)) {
 		clock++;

@@ -149,6 +164,9 @@ static void __update_sched_clock(struct 
 	 */
 	max_clock = scd->tick_gtod + (2 + delta_jiffies) * TICK_NSEC;
 
+	delta *= scd->multi;
+	delta >>= MULTI_SHIFT;
+
 	if (unlikely(clock + delta > max_clock) && check_max(scd)) {
 		if (clock < max_clock)
 			clock = max_clock;

@@ -230,6 +248,7 @@ void sched_clock_tick(void)
 {
 	struct sched_clock_data *scd = this_scd();
 	unsigned long now_jiffies = jiffies;
+	s64 mult, delta_gtod, delta_raw;
 	u64 now, now_gtod;
 
 	if (unlikely(!sched_clock_running))

@@ -247,9 +266,23 @@ void sched_clock_tick(void)
 	 * already observe 1 new jiffy; adding a new tick_gtod to that would
 	 * increase the clock 2 jiffies.
 	 */
-	scd->tick_jiffies = now_jiffies;
+	delta_gtod = now_gtod - scd->tick_gtod;
+	delta_raw = now - scd->tick_raw;
+
+	if ((long)delta_raw > 0) {
+		mult = delta_gtod << MULTI_SHIFT;
+		do_div(mult, delta_raw);
+		scd->multi = mult;
+		if (scd->multi > MAX_MULTI)
+			scd->multi = MAX_MULTI;
+		else if (scd->multi < MIN_MULTI)
+			scd->multi = MIN_MULTI;
+	} else
+		scd->multi = 1 << MULTI_SHIFT;
+
 	scd->tick_raw = now;
 	scd->tick_gtod = now_gtod;
+	scd->tick_jiffies = now_jiffies;
 	__raw_spin_unlock(&scd->lock);
 }
 

@@ -279,6 +312,7 @@ void sched_clock_idle_wakeup_event(u64 d
 	__raw_spin_lock(&scd->lock);
 	scd->prev_raw = now;
 	scd->clock += delta_ns;
+	scd->multi = 1 << MULTI_SHIFT;
 	__raw_spin_unlock(&scd->lock);
 
 	touch_softlockup_watchdog();