sched clock: couple local and remote clocks
When taking the time of a remote CPU, use the opportunity to couple (sync) the clocks to each other. (in a monotonic way) Signed-off-by: Ingo Molnar <mingo@elte.hu> Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Acked-by: Mike Galbraith <efault@gmx.de>
This commit is contained in:
parent
56b906126d
commit
4a273f209c
|
@ -149,7 +149,7 @@ static void lock_double_clock(struct sched_clock_data *data1,
|
||||||
u64 sched_clock_cpu(int cpu)
|
u64 sched_clock_cpu(int cpu)
|
||||||
{
|
{
|
||||||
struct sched_clock_data *scd = cpu_sdc(cpu);
|
struct sched_clock_data *scd = cpu_sdc(cpu);
|
||||||
u64 now, clock;
|
u64 now, clock, this_clock, remote_clock;
|
||||||
|
|
||||||
if (unlikely(!sched_clock_running))
|
if (unlikely(!sched_clock_running))
|
||||||
return 0ull;
|
return 0ull;
|
||||||
|
@ -158,26 +158,36 @@ u64 sched_clock_cpu(int cpu)
|
||||||
now = sched_clock();
|
now = sched_clock();
|
||||||
|
|
||||||
if (cpu != raw_smp_processor_id()) {
|
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();
|
struct sched_clock_data *my_scd = this_scd();
|
||||||
|
|
||||||
lock_double_clock(scd, my_scd);
|
lock_double_clock(scd, my_scd);
|
||||||
|
|
||||||
now += scd->tick_raw - my_scd->tick_raw;
|
this_clock = __update_sched_clock(my_scd, now);
|
||||||
now += my_scd->tick_gtod - scd->tick_gtod;
|
remote_clock = scd->clock;
|
||||||
|
|
||||||
|
/*
|
||||||
|
* 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);
|
__raw_spin_unlock(&my_scd->lock);
|
||||||
} else {
|
} else {
|
||||||
__raw_spin_lock(&scd->lock);
|
__raw_spin_lock(&scd->lock);
|
||||||
|
clock = __update_sched_clock(scd, now);
|
||||||
}
|
}
|
||||||
|
|
||||||
clock = __update_sched_clock(scd, now);
|
|
||||||
|
|
||||||
__raw_spin_unlock(&scd->lock);
|
__raw_spin_unlock(&scd->lock);
|
||||||
|
|
||||||
return clock;
|
return clock;
|
||||||
|
@ -223,7 +233,6 @@ EXPORT_SYMBOL_GPL(sched_clock_idle_sleep_event);
|
||||||
void sched_clock_idle_wakeup_event(u64 delta_ns)
|
void sched_clock_idle_wakeup_event(u64 delta_ns)
|
||||||
{
|
{
|
||||||
struct sched_clock_data *scd = this_scd();
|
struct sched_clock_data *scd = this_scd();
|
||||||
u64 now = sched_clock();
|
|
||||||
|
|
||||||
/*
|
/*
|
||||||
* Override the previous timestamp and ignore all
|
* Override the previous timestamp and ignore all
|
||||||
|
|
Loading…
Reference in a new issue