summaryrefslogtreecommitdiffstats
path: root/kernel/sched_clock.c
diff options
context:
space:
mode:
Diffstat (limited to 'kernel/sched_clock.c')
-rw-r--r--kernel/sched_clock.c124
1 files changed, 105 insertions, 19 deletions
diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c
index 60094e257a9a..22ed55d1167f 100644
--- a/kernel/sched_clock.c
+++ b/kernel/sched_clock.c
@@ -3,6 +3,9 @@
*
* Copyright (C) 2008 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
*
+ * Updates and enhancements:
+ * Copyright (C) 2008 Red Hat, Inc. Steven Rostedt <srostedt@redhat.com>
+ *
* Based on code by:
* Ingo Molnar <mingo@redhat.com>
* Guillaume Chazarain <guichaz@gmail.com>
@@ -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
@@ -40,11 +48,15 @@ struct sched_clock_data {
*/
raw_spinlock_t lock;
- unsigned long prev_jiffies;
+ unsigned long tick_jiffies;
u64 prev_raw;
u64 tick_raw;
u64 tick_gtod;
u64 clock;
+ s64 multi;
+#ifdef CONFIG_NO_HZ
+ int check_max;
+#endif
};
static DEFINE_PER_CPU_SHARED_ALIGNED(struct sched_clock_data, sched_clock_data);
@@ -71,41 +83,91 @@ void sched_clock_init(void)
struct sched_clock_data *scd = cpu_sdc(cpu);
scd->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
- scd->prev_jiffies = now_jiffies;
+ scd->tick_jiffies = now_jiffies;
scd->prev_raw = 0;
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
}
sched_clock_running = 1;
}
+#ifdef CONFIG_NO_HZ
+/*
+ * The dynamic ticks makes the delta jiffies inaccurate. This
+ * prevents us from checking the maximum time update.
+ * Disable the maximum check during stopped ticks.
+ */
+void sched_clock_tick_stop(int cpu)
+{
+ struct sched_clock_data *scd = cpu_sdc(cpu);
+
+ scd->check_max = 0;
+}
+
+void sched_clock_tick_start(int cpu)
+{
+ struct sched_clock_data *scd = cpu_sdc(cpu);
+
+ scd->check_max = 1;
+}
+
+static int check_max(struct sched_clock_data *scd)
+{
+ return scd->check_max;
+}
+#else
+static int check_max(struct sched_clock_data *scd)
+{
+ return 1;
+}
+#endif /* CONFIG_NO_HZ */
+
/*
* update the percpu scd from the raw @now value
*
* - 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->prev_jiffies;
+ long delta_jiffies = now_jiffies - scd->tick_jiffies;
u64 clock = scd->clock;
u64 min_clock, max_clock;
s64 delta = now - scd->prev_raw;
WARN_ON_ONCE(!irqs_disabled());
- min_clock = scd->tick_gtod + delta_jiffies * 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++;
goto out;
}
- max_clock = min_clock + TICK_NSEC;
+ /*
+ * The clock must stay within a jiffie of the gtod.
+ * But since we may be at the start of a jiffy or the end of one
+ * we add another jiffy buffer.
+ */
+ max_clock = scd->tick_gtod + (2 + delta_jiffies) * TICK_NSEC;
+
+ delta *= scd->multi;
+ delta >>= MULTI_SHIFT;
- if (unlikely(clock + delta > max_clock)) {
+ if (unlikely(clock + delta > max_clock) && check_max(scd)) {
if (clock < max_clock)
clock = max_clock;
else
@@ -118,9 +180,12 @@ static void __update_sched_clock(struct sched_clock_data *scd, u64 now)
if (unlikely(clock < min_clock))
clock = min_clock;
- scd->prev_raw = now;
- scd->prev_jiffies = now_jiffies;
- 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,
@@ -160,25 +225,30 @@ u64 sched_clock_cpu(int cpu)
now -= my_scd->tick_raw;
now += scd->tick_raw;
- now -= my_scd->tick_gtod;
- now += scd->tick_gtod;
+ now += my_scd->tick_gtod;
+ 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;
}
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))
@@ -186,18 +256,33 @@ 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);
+ __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
* increase the clock 2 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);
}
@@ -227,6 +312,7 @@ void sched_clock_idle_wakeup_event(u64 delta_ns)
__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();
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-18 22:21:11 +0000