X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=kernel%2Fsched_clock.c;h=a0b0852414cc599169efd81c5789f03ee50dad8b;hb=f6490438fce5902f840d1f0f905295077c635e7a;hp=b96559cb96a52153e27513a4fb7940e0fbfae8af;hpb=50526968e99afbca34924abcb04658b6dd5c5ea5;p=safe%2Fjmp%2Flinux-2.6 diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c index b96559c..a0b0852 100644 --- a/kernel/sched_clock.c +++ b/kernel/sched_clock.c @@ -12,19 +12,17 @@ * * Create a semi stable clock from a mixture of other events, including: * - gtod - * - jiffies * - sched_clock() * - explicit idle events * * We use gtod as base and the unstable clock deltas. The deltas are filtered, - * making it monotonic and keeping it within an expected window. This window - * is set up using jiffies. + * making it monotonic and keeping it within an expected window. * * Furthermore, explicit sleep and wakeup hooks allow us to account for time * that is otherwise invisible (TSC gets stopped). * * The clock: sched_clock_cpu() is monotonic per cpu, and should be somewhat - * consistent between cpus (never more than 1 jiffies difference). + * consistent between cpus (never more than 2 jiffies difference). */ #include #include @@ -42,6 +40,8 @@ unsigned long long __attribute__((weak)) sched_clock(void) return (unsigned long long)jiffies * (NSEC_PER_SEC / HZ); } +static __read_mostly int sched_clock_running; + #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK struct sched_clock_data { @@ -52,8 +52,6 @@ struct sched_clock_data { */ raw_spinlock_t lock; - unsigned long tick_jiffies; - u64 prev_raw; u64 tick_raw; u64 tick_gtod; u64 clock; @@ -71,20 +69,15 @@ static inline struct sched_clock_data *cpu_sdc(int cpu) 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()); - unsigned long now_jiffies = jiffies; int cpu; for_each_possible_cpu(cpu) { struct sched_clock_data *scd = cpu_sdc(cpu); 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; @@ -94,45 +87,51 @@ void sched_clock_init(void) } /* + * min,max except they take wrapping into account + */ + +static inline u64 wrap_min(u64 x, u64 y) +{ + return (s64)(x - y) < 0 ? x : y; +} + +static inline u64 wrap_max(u64 x, u64 y) +{ + return (s64)(x - y) > 0 ? x : y; +} + +/* * 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 + * - use the GTOD tick value to create a window to filter crazy TSC values */ -static void __update_sched_clock(struct sched_clock_data *scd, u64 now) +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; + u64 clock, min_clock, max_clock; WARN_ON_ONCE(!irqs_disabled()); - min_clock = scd->tick_gtod + delta_jiffies * TICK_NSEC; - if (unlikely(delta < 0)) { - clock++; - goto out; - } + if (unlikely(delta < 0)) + delta = 0; - max_clock = min_clock + TICK_NSEC; + /* + * scd->clock = clamp(scd->tick_gtod + delta, + * max(scd->tick_gtod, scd->clock), + * scd->tick_gtod + TICK_NSEC); + */ - if (unlikely(clock + delta > max_clock)) { - if (clock < max_clock) - clock = max_clock; - else - clock++; - } else { - clock += delta; - } + 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); - out: - if (unlikely(clock < min_clock)) - clock = min_clock; + clock = wrap_max(clock, min_clock); + clock = wrap_min(clock, max_clock); - scd->prev_raw = now; - scd->tick_jiffies = now_jiffies; scd->clock = clock; + + return scd->clock; } static void lock_double_clock(struct sched_clock_data *data1, @@ -150,7 +149,7 @@ 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; @@ -159,27 +158,36 @@ u64 sched_clock_cpu(int cpu) 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 += scd->tick_raw - my_scd->tick_raw; - now += my_scd->tick_gtod - scd->tick_gtod; + this_clock = __update_sched_clock(my_scd, now); + 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)) { + 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); } - __update_sched_clock(scd, now); - clock = scd->clock; - __raw_spin_unlock(&scd->lock); return clock; @@ -199,14 +207,9 @@ void sched_clock_tick(void) now = sched_clock(); __raw_spin_lock(&scd->lock); - __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. - */ scd->tick_raw = now; scd->tick_gtod = now_gtod; + __update_sched_clock(scd, now); __raw_spin_unlock(&scd->lock); } @@ -224,24 +227,29 @@ EXPORT_SYMBOL_GPL(sched_clock_idle_sleep_event); */ 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 - * sched_clock() deltas that occured while we idled, - * and use the PM-provided delta_ns to advance the - * rq clock: - */ - __raw_spin_lock(&scd->lock); - scd->prev_raw = now; - scd->clock += delta_ns; - __raw_spin_unlock(&scd->lock); + if (timekeeping_suspended) + return; + sched_clock_tick(); touch_softlockup_watchdog(); } EXPORT_SYMBOL_GPL(sched_clock_idle_wakeup_event); +#else /* CONFIG_HAVE_UNSTABLE_SCHED_CLOCK */ + +void sched_clock_init(void) +{ + 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)