diff options
| -rw-r--r-- | Documentation/time_interpolators.txt | 41 | ||||
| -rw-r--r-- | include/linux/timex.h | 60 | ||||
| -rw-r--r-- | kernel/time.c | 88 | ||||
| -rw-r--r-- | kernel/time/ntp.c | 10 | ||||
| -rw-r--r-- | kernel/time/timekeeping.c | 4 | ||||
| -rw-r--r-- | kernel/timer.c | 188 |
6 files changed, 0 insertions, 391 deletions
diff --git a/Documentation/time_interpolators.txt b/Documentation/time_interpolators.txt deleted file mode 100644 index e3b60854fbc2..000000000000 --- a/Documentation/time_interpolators.txt +++ /dev/null @@ -1,41 +0,0 @@ -Time Interpolators ------------------- - -Time interpolators are a base of time calculation between timer ticks and -allow an accurate determination of time down to the accuracy of the time -source in nanoseconds. - -The architecture specific code typically provides gettimeofday and -settimeofday under Linux. The time interpolator provides both if an arch -defines CONFIG_TIME_INTERPOLATION. The arch still must set up timer tick -operations and call the necessary functions to advance the clock. - -With the time interpolator a standardized interface exists for time -interpolation between ticks. The provided logic is highly scalable -and has been tested in SMP situations of up to 512 CPUs. - -If CONFIG_TIME_INTERPOLATION is defined then the architecture specific code -(or the device drivers - like HPET) may register time interpolators. -These are typically defined in the following way: - -static struct time_interpolator my_interpolator { - .frequency = MY_FREQUENCY, - .source = TIME_SOURCE_MMIO32, - .shift = 8, /* scaling for higher accuracy */ - .drift = -1, /* Unknown drift */ - .jitter = 0 /* time source is stable */ -}; - -void time_init(void) -{ - .... - /* Initialization of the timer *. - my_interpolator.address = &my_timer; - register_time_interpolator(&my_interpolator); - .... -} - -For more details see include/linux/timex.h and kernel/timer.c. - -Christoph Lameter <christoph@lameter.com>, October 31, 2004 - diff --git a/include/linux/timex.h b/include/linux/timex.h index da929dbbea2a..37ac3ff90faf 100644 --- a/include/linux/timex.h +++ b/include/linux/timex.h @@ -224,66 +224,6 @@ static inline int ntp_synced(void) __x < 0 ? -(-__x >> __s) : __x >> __s; \ }) - -#ifdef CONFIG_TIME_INTERPOLATION - -#define TIME_SOURCE_CPU 0 -#define TIME_SOURCE_MMIO64 1 -#define TIME_SOURCE_MMIO32 2 -#define TIME_SOURCE_FUNCTION 3 - -/* For proper operations time_interpolator clocks must run slightly slower - * than the standard clock since the interpolator may only correct by having - * time jump forward during a tick. A slower clock is usually a side effect - * of the integer divide of the nanoseconds in a second by the frequency. - * The accuracy of the division can be increased by specifying a shift. - * However, this may cause the clock not to be slow enough. - * The interpolator will self-tune the clock by slowing down if no - * resets occur or speeding up if the time jumps per analysis cycle - * become too high. - * - * Setting jitter compensates for a fluctuating timesource by comparing - * to the last value read from the timesource to insure that an earlier value - * is not returned by a later call. The price to pay - * for the compensation is that the timer routines are not as scalable anymore. - */ - -struct time_interpolator { - u16 source; /* time source flags */ - u8 shift; /* increases accuracy of multiply by shifting. */ - /* Note that bits may be lost if shift is set too high */ - u8 jitter; /* if set compensate for fluctuations */ - u32 nsec_per_cyc; /* set by register_time_interpolator() */ - void *addr; /* address of counter or function */ - cycles_t mask; /* mask the valid bits of the counter */ - unsigned long offset; /* nsec offset at last update of interpolator */ - u64 last_counter; /* counter value in units of the counter at last update */ - cycles_t last_cycle; /* Last timer value if TIME_SOURCE_JITTER is set */ - u64 frequency; /* frequency in counts/second */ - long drift; /* drift in parts-per-million (or -1) */ - unsigned long skips; /* skips forward */ - unsigned long ns_skipped; /* nanoseconds skipped */ - struct time_interpolator *next; -}; - -extern void register_time_interpolator(struct time_interpolator *); -extern void unregister_time_interpolator(struct time_interpolator *); -extern void time_interpolator_reset(void); -extern unsigned long time_interpolator_get_offset(void); -extern void time_interpolator_update(long delta_nsec); - -#else /* !CONFIG_TIME_INTERPOLATION */ - -static inline void time_interpolator_reset(void) -{ -} - -static inline void time_interpolator_update(long delta_nsec) -{ -} - -#endif /* !CONFIG_TIME_INTERPOLATION */ - #define TICK_LENGTH_SHIFT 32 #ifdef CONFIG_NO_HZ diff --git a/kernel/time.c b/kernel/time.c index ffe19149d770..e325597f5bf5 100644 --- a/kernel/time.c +++ b/kernel/time.c @@ -136,7 +136,6 @@ static inline void warp_clock(void) write_seqlock_irq(&xtime_lock); wall_to_monotonic.tv_sec -= sys_tz.tz_minuteswest * 60; xtime.tv_sec += sys_tz.tz_minuteswest * 60; - time_interpolator_reset(); write_sequnlock_irq(&xtime_lock); clock_was_set(); } @@ -309,92 +308,6 @@ struct timespec timespec_trunc(struct timespec t, unsigned gran) } EXPORT_SYMBOL(timespec_trunc); -#ifdef CONFIG_TIME_INTERPOLATION -void getnstimeofday (struct timespec *tv) -{ - unsigned long seq,sec,nsec; - - do { - seq = read_seqbegin(&xtime_lock); - sec = xtime.tv_sec; - nsec = xtime.tv_nsec+time_interpolator_get_offset(); - } while (unlikely(read_seqretry(&xtime_lock, seq))); - - while (unlikely(nsec >= NSEC_PER_SEC)) { - nsec -= NSEC_PER_SEC; - ++sec; - } - tv->tv_sec = sec; - tv->tv_nsec = nsec; -} -EXPORT_SYMBOL_GPL(getnstimeofday); - -int do_settimeofday (struct timespec *tv) -{ - time_t wtm_sec, sec = tv->tv_sec; - long wtm_nsec, nsec = tv->tv_nsec; - - if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC) - return -EINVAL; - - write_seqlock_irq(&xtime_lock); - { - wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec); - wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec); - - set_normalized_timespec(&xtime, sec, nsec); - set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec); - - time_adjust = 0; /* stop active adjtime() */ - time_status |= STA_UNSYNC; - time_maxerror = NTP_PHASE_LIMIT; - time_esterror = NTP_PHASE_LIMIT; - time_interpolator_reset(); - } - write_sequnlock_irq(&xtime_lock); - clock_was_set(); - return 0; -} -EXPORT_SYMBOL(do_settimeofday); - -void do_gettimeofday (struct timeval *tv) -{ - unsigned long seq, nsec, usec, sec, offset; - do { - seq = read_seqbegin(&xtime_lock); - offset = time_interpolator_get_offset(); - sec = xtime.tv_sec; - nsec = xtime.tv_nsec; - } while (unlikely(read_seqretry(&xtime_lock, seq))); - - usec = (nsec + offset) / 1000; - - while (unlikely(usec >= USEC_PER_SEC)) { - usec -= USEC_PER_SEC; - ++sec; - } - - tv->tv_sec = sec; - tv->tv_usec = usec; - - /* - * Make sure xtime.tv_sec [returned by sys_time()] always - * follows the gettimeofday() result precisely. This - * condition is extremely unlikely, it can hit at most - * once per second: - */ - if (unlikely(xtime.tv_sec != tv->tv_sec)) { - unsigned long flags; - - write_seqlock_irqsave(&xtime_lock, flags); - update_wall_time(); - write_sequnlock_irqrestore(&xtime_lock, flags); - } -} -EXPORT_SYMBOL(do_gettimeofday); - -#else /* CONFIG_TIME_INTERPOLATION */ - #ifndef CONFIG_GENERIC_TIME /* * Simulate gettimeofday using do_gettimeofday which only allows a timeval @@ -410,7 +323,6 @@ void getnstimeofday(struct timespec *tv) } EXPORT_SYMBOL_GPL(getnstimeofday); #endif -#endif /* CONFIG_TIME_INTERPOLATION */ /* Converts Gregorian date to seconds since 1970-01-01 00:00:00. * Assumes input in normal date format, i.e. 1980-12-31 23:59:59 diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c index 438c6b723ee2..b5e352597cbb 100644 --- a/kernel/time/ntp.c +++ b/kernel/time/ntp.c @@ -116,11 +116,6 @@ void second_overflow(void) if (xtime.tv_sec % 86400 == 0) { xtime.tv_sec--; wall_to_monotonic.tv_sec++; - /* - * The timer interpolator will make time change - * gradually instead of an immediate jump by one second - */ - time_interpolator_update(-NSEC_PER_SEC); time_state = TIME_OOP; printk(KERN_NOTICE "Clock: inserting leap second " "23:59:60 UTC\n"); @@ -130,11 +125,6 @@ void second_overflow(void) if ((xtime.tv_sec + 1) % 86400 == 0) { xtime.tv_sec++; wall_to_monotonic.tv_sec--; - /* - * Use of time interpolator for a gradual change of - * time - */ - time_interpolator_update(NSEC_PER_SEC); time_state = TIME_WAIT; printk(KERN_NOTICE "Clock: deleting leap second " "23:59:59 UTC\n"); diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index 728cedfd3cbd..027d46c906e0 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -466,10 +466,6 @@ void update_wall_time(void) second_overflow(); } - /* interpolator bits */ - time_interpolator_update(clock->xtime_interval - >> clock->shift); - /* accumulate error between NTP and clock interval */ clock->error += current_tick_length(); clock->error -= clock->xtime_interval << (TICK_LENGTH_SHIFT - clock->shift); diff --git a/kernel/timer.c b/kernel/timer.c index b7792fb03387..dbc03ab14eed 100644 --- a/kernel/timer.c +++ b/kernel/timer.c @@ -1349,194 +1349,6 @@ void __init init_timers(void) open_softirq(TIMER_SOFTIRQ, run_timer_softirq, NULL); } -#ifdef CONFIG_TIME_INTERPOLATION - -struct time_interpolator *time_interpolator __read_mostly; -static struct time_interpolator *time_interpolator_list __read_mostly; -static DEFINE_SPINLOCK(time_interpolator_lock); - -static inline cycles_t time_interpolator_get_cycles(unsigned int src) -{ - unsigned long (*x)(void); - - switch (src) - { - case TIME_SOURCE_FUNCTION: - x = time_interpolator->addr; - return x(); - - case TIME_SOURCE_MMIO64 : - return readq_relaxed((void __iomem *)time_interpolator->addr); - - case TIME_SOURCE_MMIO32 : - return readl_relaxed((void __iomem *)time_interpolator->addr); - - default: return get_cycles(); - } -} - -static inline u64 time_interpolator_get_counter(int writelock) -{ - unsigned int src = time_interpolator->source; - - if (time_interpolator->jitter) - { - cycles_t lcycle; - cycles_t now; - - do { - lcycle = time_interpolator->last_cycle; - now = time_interpolator_get_cycles(src); - if (lcycle && time_after(lcycle, now)) - return lcycle; - - /* When holding the xtime write lock, there's no need - * to add the overhead of the cmpxchg. Readers are - * force to retry until the write lock is released. - */ - if (writelock) { - time_interpolator->last_cycle = now; - return now; - } - /* Keep track of the last timer value returned. The use of cmpxchg here - * will cause contention in an SMP environment. - */ - } while (unlikely(cmpxchg(&time_interpolator->last_cycle, lcycle, now) != lcycle)); - return now; - } - else - return time_interpolator_get_cycles(src); -} - -void time_interpolator_reset(void) -{ - time_interpolator->offset = 0; - time_interpolator->last_counter = time_interpolator_get_counter(1); -} - -#define GET_TI_NSECS(count,i) (((((count) - i->last_counter) & (i)->mask) * (i)->nsec_per_cyc) >> (i)->shift) - -unsigned long time_interpolator_get_offset(void) -{ - /* If we do not have a time interpolator set up then just return zero */ - if (!time_interpolator) - return 0; - - return time_interpolator->offset + - GET_TI_NSECS(time_interpolator_get_counter(0), time_interpolator); -} - -#define INTERPOLATOR_ADJUST 65536 -#define INTERPOLATOR_MAX_SKIP 10*INTERPOLATOR_ADJUST - -void time_interpolator_update(long delta_nsec) -{ - u64 counter; - unsigned long offset; - - /* If there is no time interpolator set up then do nothing */ - if (!time_interpolator) - return; - - /* - * The interpolator compensates for late ticks by accumulating the late - * time in time_interpolator->offset. A tick earlier than expected will - * lead to a reset of the offset and a corresponding jump of the clock - * forward. Again this only works if the interpolator clock is running - * slightly slower than the regular clock and the tuning logic insures - * that. - */ - - counter = time_interpolator_get_counter(1); - offset = time_interpolator->offset + - GET_TI_NSECS(counter, time_interpolator); - - if (delta_nsec < 0 || (unsigned long) delta_nsec < offset) - time_interpolator->offset = offset - delta_nsec; - else { - time_interpolator->skips++; - time_interpolator->ns_skipped += delta_nsec - offset; - time_interpolator->offset = 0; - } - time_interpolator->last_counter = counter; - - /* Tuning logic for time interpolator invoked every minute or so. - * Decrease interpolator clock speed if no skips occurred and an offset is carried. - * Increase interpolator clock speed if we skip too much time. - */ - if (jiffies % INTERPOLATOR_ADJUST == 0) - { - if (time_interpolator->skips == 0 && time_interpolator->offset > tick_nsec) - time_interpolator->nsec_per_cyc--; - if (time_interpolator->ns_skipped > INTERPOLATOR_MAX_SKIP && time_interpolator->offset == 0) - time_interpolator->nsec_per_cyc++; - time_interpolator->skips = 0; - time_interpolator->ns_skipped = 0; - } -} - -static inline int -is_better_time_interpolator(struct time_interpolator *new) -{ - if (!time_interpolator) - return 1; - return new->frequency > 2*time_interpolator->frequency || - (unsigned long)new->drift < (unsigned long)time_interpolator->drift; -} - -void -register_time_interpolator(struct time_interpolator *ti) -{ - unsigned long flags; - - /* Sanity check */ - BUG_ON(ti->frequency == 0 || ti->mask == 0); - - ti->nsec_per_cyc = ((u64)NSEC_PER_SEC << ti->shift) / ti->frequency; - spin_lock(&time_interpolator_lock); - write_seqlock_irqsave(&xtime_lock, flags); - if (is_better_time_interpolator(ti)) { - time_interpolator = ti; - time_interpolator_reset(); - } - write_sequnlock_irqrestore(&xtime_lock, flags); - - ti->next = time_interpolator_list; - time_interpolator_list = ti; - spin_unlock(&time_interpolator_lock); -} - -void -unregister_time_interpolator(struct time_interpolator *ti) -{ - struct time_interpolator *curr, **prev; - unsigned long flags; - - spin_lock(&time_interpolator_lock); - prev = &time_interpolator_list; - for (curr = *prev; curr; curr = curr->next) { - if (curr == ti) { - *prev = curr->next; - break; - } - prev = &curr->next; - } - - write_seqlock_irqsave(&xtime_lock, flags); - if (ti == time_interpolator) { - /* we lost the best time-interpolator: */ - time_interpolator = NULL; - /* find the next-best interpolator */ - for (curr = time_interpolator_list; curr; curr = curr->next) - if (is_better_time_interpolator(curr)) - time_interpolator = curr; - time_interpolator_reset(); - } - write_sequnlock_irqrestore(&xtime_lock, flags); - spin_unlock(&time_interpolator_lock); -} -#endif /* CONFIG_TIME_INTERPOLATION */ - /** * msleep - sleep safely even with waitqueue interruptions * @msecs: Time in milliseconds to sleep for |
