X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=kernel%2Fsched_clock.c;h=5b496132c28a1baca2a6353c6a6b0216a0f02508;hb=a0de055cf61338549b13079a5677ef2e1b6472ef;hp=a0b0852414cc599169efd81c5789f03ee50dad8b;hpb=1c5745aa380efb6417b5681104b007c8612fb496;p=safe%2Fjmp%2Flinux-2.6 diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c index a0b0852..5b49613 100644 --- a/kernel/sched_clock.c +++ b/kernel/sched_clock.c @@ -24,11 +24,12 @@ * The clock: sched_clock_cpu() is monotonic per cpu, and should be somewhat * consistent between cpus (never more than 2 jiffies difference). */ -#include -#include #include -#include +#include #include +#include +#include +#include /* * Scheduler clock - returns current time in nanosec units. @@ -37,21 +38,16 @@ */ unsigned long long __attribute__((weak)) sched_clock(void) { - return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ); + return (unsigned long long)(jiffies - INITIAL_JIFFIES) + * (NSEC_PER_SEC / HZ); } static __read_mostly int sched_clock_running; #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK +__read_mostly int sched_clock_stable; struct sched_clock_data { - /* - * Raw spinlock - this is a special case: this might be called - * from within instrumentation code so we dont want to do any - * instrumentation ourselves. - */ - raw_spinlock_t lock; - u64 tick_raw; u64 tick_gtod; u64 clock; @@ -77,7 +73,6 @@ void sched_clock_init(void) for_each_possible_cpu(cpu) { struct sched_clock_data *scd = cpu_sdc(cpu); - scd->lock = (raw_spinlock_t)__RAW_SPIN_LOCK_UNLOCKED; scd->tick_raw = 0; scd->tick_gtod = ktime_now; scd->clock = ktime_now; @@ -87,7 +82,7 @@ void sched_clock_init(void) } /* - * min,max except they take wrapping into account + * min, max except they take wrapping into account */ static inline u64 wrap_min(u64 x, u64 y) @@ -106,111 +101,117 @@ static inline u64 wrap_max(u64 x, u64 y) * - filter out backward motion * - use the GTOD tick value to create a window to filter crazy TSC values */ -static u64 __update_sched_clock(struct sched_clock_data *scd, u64 now) +static u64 sched_clock_local(struct sched_clock_data *scd) { - s64 delta = now - scd->tick_raw; - u64 clock, min_clock, max_clock; - - WARN_ON_ONCE(!irqs_disabled()); + u64 now, clock, old_clock, min_clock, max_clock; + s64 delta; +again: + now = sched_clock(); + delta = now - scd->tick_raw; if (unlikely(delta < 0)) delta = 0; + old_clock = scd->clock; + /* * scd->clock = clamp(scd->tick_gtod + delta, - * max(scd->tick_gtod, scd->clock), - * scd->tick_gtod + TICK_NSEC); + * max(scd->tick_gtod, scd->clock), + * scd->tick_gtod + TICK_NSEC); */ clock = scd->tick_gtod + delta; - min_clock = wrap_max(scd->tick_gtod, scd->clock); - max_clock = wrap_max(scd->clock, scd->tick_gtod + TICK_NSEC); + min_clock = wrap_max(scd->tick_gtod, old_clock); + max_clock = wrap_max(old_clock, scd->tick_gtod + TICK_NSEC); clock = wrap_max(clock, min_clock); clock = wrap_min(clock, max_clock); - scd->clock = clock; + if (cmpxchg64(&scd->clock, old_clock, clock) != old_clock) + goto again; - return scd->clock; + return clock; } -static void lock_double_clock(struct sched_clock_data *data1, - struct sched_clock_data *data2) +static u64 sched_clock_remote(struct sched_clock_data *scd) { - if (data1 < data2) { - __raw_spin_lock(&data1->lock); - __raw_spin_lock(&data2->lock); + struct sched_clock_data *my_scd = this_scd(); + u64 this_clock, remote_clock; + u64 *ptr, old_val, val; + + sched_clock_local(my_scd); +again: + this_clock = my_scd->clock; + 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((s64)(remote_clock - this_clock) < 0)) { + ptr = &scd->clock; + old_val = remote_clock; + val = this_clock; } else { - __raw_spin_lock(&data2->lock); - __raw_spin_lock(&data1->lock); + /* + * Should be rare, but possible: + */ + ptr = &my_scd->clock; + old_val = this_clock; + val = remote_clock; } + + if (cmpxchg64(ptr, old_val, val) != old_val) + goto again; + + return val; } u64 sched_clock_cpu(int cpu) { - struct sched_clock_data *scd = cpu_sdc(cpu); - u64 now, clock, this_clock, remote_clock; - - if (unlikely(!sched_clock_running)) - return 0ull; + struct sched_clock_data *scd; + u64 clock; WARN_ON_ONCE(!irqs_disabled()); - now = sched_clock(); - - if (cpu != raw_smp_processor_id()) { - struct sched_clock_data *my_scd = this_scd(); - lock_double_clock(scd, my_scd); + if (sched_clock_stable) + return sched_clock(); - this_clock = __update_sched_clock(my_scd, now); - remote_clock = scd->clock; + if (unlikely(!sched_clock_running)) + return 0ull; - /* - * 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((s64)(remote_clock - this_clock) < 0)) { - 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); - } else { - __raw_spin_lock(&scd->lock); - clock = __update_sched_clock(scd, now); - } + scd = cpu_sdc(cpu); - __raw_spin_unlock(&scd->lock); + if (cpu != smp_processor_id()) + clock = sched_clock_remote(scd); + else + clock = sched_clock_local(scd); return clock; } void sched_clock_tick(void) { - struct sched_clock_data *scd = this_scd(); + struct sched_clock_data *scd; u64 now, now_gtod; + if (sched_clock_stable) + return; + if (unlikely(!sched_clock_running)) return; WARN_ON_ONCE(!irqs_disabled()); + scd = this_scd(); now_gtod = ktime_to_ns(ktime_get()); now = sched_clock(); - __raw_spin_lock(&scd->lock); scd->tick_raw = now; scd->tick_gtod = now_gtod; - __update_sched_clock(scd, now); - __raw_spin_unlock(&scd->lock); + sched_clock_local(scd); } /* @@ -235,6 +236,18 @@ void sched_clock_idle_wakeup_event(u64 delta_ns) } EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event); +unsigned long long cpu_clock(int cpu) +{ + unsigned long long clock; + unsigned long flags; + + local_irq_save(flags); + clock = sched_clock_cpu(cpu); + local_irq_restore(flags); + + return clock; +} + #else /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */ void sched_clock_init(void) @@ -250,17 +263,12 @@ u64 sched_clock_cpu(int cpu) return sched_clock(); } -#endif unsigned long long cpu_clock(int cpu) { - unsigned long long clock; - unsigned long flags; + return sched_clock_cpu(cpu); +} - local_irq_save(flags); - clock = sched_clock_cpu(cpu); - local_irq_restore(flags); +#endif /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */ - return clock; -} EXPORT_SYMBOL_GPL(cpu_clock);