#include <linux/ktime.h>
#include <linux/module.h>
+/*
+ * Scheduler clock - returns current time in nanosec units.
+ * This is default implementation.
+ * Architectures and sub-architectures can override this.
+ */
+unsigned long long __attribute__((weak)) sched_clock(void)
+{
+ return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ);
+}
-#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
+static __read_mostly int sched_clock_running;
-#define MULTI_SHIFT 15
-/* Max is double, Min is 1/2 */
-#define MAX_MULTI (2LL << MULTI_SHIFT)
-#define MIN_MULTI (1LL << (MULTI_SHIFT-1))
+#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
struct sched_clock_data {
/*
raw_spinlock_t lock;
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);
return &per_cpu(sched_clock_data, cpu);
}
-static __read_mostly int sched_clock_running;
-
void sched_clock_init(void)
{
u64 ktime_now = ktime_to_ns(ktime_get());
scd->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED;
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, u64 *time)
+static u64 __update_sched_clock(struct sched_clock_data *scd, u64 now)
{
unsigned long now_jiffies = jiffies;
long delta_jiffies = now_jiffies - scd->tick_jiffies;
u64 clock = scd->clock;
u64 min_clock, max_clock;
- s64 delta = now - scd->prev_raw;
+ s64 delta = now - scd->tick_raw;
WARN_ON_ONCE(!irqs_disabled());
-
- /*
- * 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;
+ min_clock = scd->tick_gtod + delta_jiffies * TICK_NSEC;
if (unlikely(delta < 0)) {
clock++;
goto out;
}
- /*
- * 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;
+ max_clock = min_clock + TICK_NSEC;
- if (unlikely(clock + delta > max_clock) && check_max(scd)) {
+ if (unlikely(clock + delta > max_clock)) {
if (clock < max_clock)
clock = max_clock;
else
if (unlikely(clock < min_clock))
clock = min_clock;
- if (time)
- *time = clock;
- else {
- scd->prev_raw = now;
- scd->clock = clock;
- }
+ scd->tick_jiffies = now_jiffies;
+ scd->clock = clock;
+
+ return clock;
}
static void lock_double_clock(struct sched_clock_data *data1,
u64 sched_clock_cpu(int cpu)
{
struct sched_clock_data *scd = cpu_sdc(cpu);
- u64 now, clock;
+ u64 now, clock, this_clock, remote_clock;
if (unlikely(!sched_clock_running))
return 0ull;
now = sched_clock();
if (cpu != raw_smp_processor_id()) {
- /*
- * in order to update a remote cpu's clock based on our
- * unstable raw time rebase it against:
- * tick_raw (offset between raw counters)
- * tick_gotd (tick offset between cpus)
- */
struct sched_clock_data *my_scd = this_scd();
lock_double_clock(scd, my_scd);
- now -= my_scd->tick_raw;
- now += scd->tick_raw;
+ this_clock = __update_sched_clock(my_scd, now);
+ remote_clock = scd->clock;
- now += my_scd->tick_gtod;
- now -= scd->tick_gtod;
+ /*
+ * Use the opportunity that we have both locks
+ * taken to couple the two clocks: we take the
+ * larger time as the latest time for both
+ * runqueues. (this creates monotonic movement)
+ */
+ if (likely(remote_clock < this_clock)) {
+ clock = this_clock;
+ scd->clock = clock;
+ } else {
+ /*
+ * Should be rare, but possible:
+ */
+ clock = remote_clock;
+ my_scd->clock = remote_clock;
+ }
__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);
+ clock = __update_sched_clock(scd, now);
}
+ __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))
now = sched_clock();
__raw_spin_lock(&scd->lock);
- __update_sched_clock(scd, now, NULL);
+ __update_sched_clock(scd, now);
/*
* 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);
}
void sched_clock_idle_wakeup_event(u64 delta_ns)
{
struct sched_clock_data *scd = this_scd();
- u64 now = sched_clock();
/*
* Override the previous timestamp and ignore all
* rq clock:
*/
__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();
}
EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event);
-#endif
+#else /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */
-/*
- * Scheduler clock - returns current time in nanosec units.
- * This is default implementation.
- * Architectures and sub-architectures can override this.
- */
-unsigned long long __attribute__((weak)) sched_clock(void)
+void sched_clock_init(void)
{
- return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ);
+ sched_clock_running = 1;
}
+u64 sched_clock_cpu(int cpu)
+{
+ if (unlikely(!sched_clock_running))
+ return 0;
+
+ return sched_clock();
+}
+
+#endif
+
unsigned long long cpu_clock(int cpu)
{
unsigned long long clock;
projects / linux-2.6-block.git / commitdiff