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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2008-06-27 07:41:15 -0400
committerIngo Molnar <mingo@elte.hu>2008-06-27 08:31:30 -0400
commit76a2a6ee8a0660a29127f05989ac59ae1ce865fa (patch)
tree93ae1dd3cc5f564fc1e9d30bcdb0cd313f67221a
parentc09595f63bb1909c5dc4dca288f4fe818561b5f3 (diff)
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: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> Cc: Mike Galbraith <efault@gmx.de> Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--kernel/sched.c76
-rw-r--r--kernel/sched_clock.c12
2 files changed, 12 insertions, 76 deletions
diff --git a/kernel/sched.c b/kernel/sched.c
index 874b6da15430..eb3454c410fa 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -818,82 +818,6 @@ static inline u64 global_rt_runtime(void)
818 return (u64)sysctl_sched_rt_runtime * NSEC_PER_USEC; 818 return (u64)sysctl_sched_rt_runtime * NSEC_PER_USEC;
819} 819}
820 820
821unsigned long long time_sync_thresh = 100000;
822
823static DEFINE_PER_CPU(unsigned long long, time_offset);
824static DEFINE_PER_CPU(unsigned long long, prev_cpu_time);
825
826/*
827 * Global lock which we take every now and then to synchronize
828 * the CPUs time. This method is not warp-safe, but it's good
829 * enough to synchronize slowly diverging time sources and thus
830 * it's good enough for tracing:
831 */
832static DEFINE_SPINLOCK(time_sync_lock);
833static unsigned long long prev_global_time;
834
835static unsigned long long __sync_cpu_clock(unsigned long long time, int cpu)
836{
837 /*
838 * We want this inlined, to not get tracer function calls
839 * in this critical section:
840 */
841 spin_acquire(&time_sync_lock.dep_map, 0, 0, _THIS_IP_);
842 __raw_spin_lock(&time_sync_lock.raw_lock);
843
844 if (time < prev_global_time) {
845 per_cpu(time_offset, cpu) += prev_global_time - time;
846 time = prev_global_time;
847 } else {
848 prev_global_time = time;
849 }
850
851 __raw_spin_unlock(&time_sync_lock.raw_lock);
852 spin_release(&time_sync_lock.dep_map, 1, _THIS_IP_);
853
854 return time;
855}
856
857static unsigned long long __cpu_clock(int cpu)
858{
859 unsigned long long now;
860
861 /*
862 * Only call sched_clock() if the scheduler has already been
863 * initialized (some code might call cpu_clock() very early):
864 */
865 if (unlikely(!scheduler_running))
866 return 0;
867
868 now = sched_clock_cpu(cpu);
869
870 return now;
871}
872
873/*
874 * For kernel-internal use: high-speed (but slightly incorrect) per-cpu
875 * clock constructed from sched_clock():
876 */
877unsigned long long cpu_clock(int cpu)
878{
879 unsigned long long prev_cpu_time, time, delta_time;
880 unsigned long flags;
881
882 local_irq_save(flags);
883 prev_cpu_time = per_cpu(prev_cpu_time, cpu);
884 time = __cpu_clock(cpu) + per_cpu(time_offset, cpu);
885 delta_time = time-prev_cpu_time;
886
887 if (unlikely(delta_time > time_sync_thresh)) {
888 time = __sync_cpu_clock(time, cpu);
889 per_cpu(prev_cpu_time, cpu) = time;
890 }
891 local_irq_restore(flags);
892
893 return time;
894}
895EXPORT_SYMBOL_GPL(cpu_clock);
896
897#ifndef prepare_arch_switch 821#ifndef prepare_arch_switch
898# define prepare_arch_switch(next) do { } while (0) 822# define prepare_arch_switch(next) do { } while (0)
899#endif 823#endif
diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c
index ce05271219ab..3c696db59452 100644
--- a/kernel/sched_clock.c
+++ b/kernel/sched_clock.c
@@ -244,3 +244,15 @@ unsigned long long __attribute__((weak)) sched_clock(void)
244{ 244{
245 return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ); 245 return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ);
246} 246}
247
248unsigned long long cpu_clock(int cpu)
249{
250 unsigned long long clock;
251 unsigned long flags;
252
253 raw_local_irq_save(flags);
254 clock = sched_clock_cpu(cpu);
255 raw_local_irq_restore(flags);
256
257 return clock;
258}