Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 76a2a6ee authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: sched_clock_cpu() based cpu_clock() 



with sched_clock_cpu() being reasonably in sync between cpus (max 1 jiffy
difference) use this to provide cpu_clock().

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent c09595f6

kernel/sched.c

+0 −76
Original line number Diff line number Diff line
@@ -818,82 +818,6 @@ static inline u64 global_rt_runtime(void) 
	return (u64)sysctl_sched_rt_runtime * NSEC_PER_USEC;

}



unsigned long long time_sync_thresh = 100000;



static DEFINE_PER_CPU(unsigned long long, time_offset);

static DEFINE_PER_CPU(unsigned long long, prev_cpu_time);



/*

 * Global lock which we take every now and then to synchronize

 * the CPUs time. This method is not warp-safe, but it's good

 * enough to synchronize slowly diverging time sources and thus

 * it's good enough for tracing:

 */

static DEFINE_SPINLOCK(time_sync_lock);

static unsigned long long prev_global_time;



static unsigned long long __sync_cpu_clock(unsigned long long time, int cpu)

{

	/*

	 * We want this inlined, to not get tracer function calls

	 * in this critical section:

	 */

	spin_acquire(&time_sync_lock.dep_map, 0, 0, _THIS_IP_);

	__raw_spin_lock(&time_sync_lock.raw_lock);



	if (time < prev_global_time) {

		per_cpu(time_offset, cpu) += prev_global_time - time;

		time = prev_global_time;

	} else {

		prev_global_time = time;

	}



	__raw_spin_unlock(&time_sync_lock.raw_lock);

	spin_release(&time_sync_lock.dep_map, 1, _THIS_IP_);



	return time;

}



static unsigned long long __cpu_clock(int cpu)

{

	unsigned long long now;



	/*

	 * Only call sched_clock() if the scheduler has already been

	 * initialized (some code might call cpu_clock() very early):

	 */

	if (unlikely(!scheduler_running))

		return 0;



	now = sched_clock_cpu(cpu);



	return now;

}



/*

 * For kernel-internal use: high-speed (but slightly incorrect) per-cpu

 * clock constructed from sched_clock():

 */

unsigned long long cpu_clock(int cpu)

{

	unsigned long long prev_cpu_time, time, delta_time;

	unsigned long flags;



	local_irq_save(flags);

	prev_cpu_time = per_cpu(prev_cpu_time, cpu);

	time = __cpu_clock(cpu) + per_cpu(time_offset, cpu);

	delta_time = time-prev_cpu_time;



	if (unlikely(delta_time > time_sync_thresh)) {

		time = __sync_cpu_clock(time, cpu);

		per_cpu(prev_cpu_time, cpu) = time;

	}

	local_irq_restore(flags);



	return time;

}

EXPORT_SYMBOL_GPL(cpu_clock);



#ifndef prepare_arch_switch

# define prepare_arch_switch(next)	do { } while (0)

#endif

kernel/sched_clock.c

+12 −0
Original line number Diff line number Diff line
@@ -244,3 +244,15 @@ unsigned long long __attribute__((weak)) sched_clock(void) 
{

	return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ);

}



unsigned long long cpu_clock(int cpu)

{

	unsigned long long clock;

	unsigned long flags;



	raw_local_irq_save(flags);

	clock = sched_clock_cpu(cpu);

	raw_local_irq_restore(flags);



	return clock;

}