diff options
author | Thomas Gleixner <tglx@linutronix.de> | 2010-02-17 18:27:37 +0100 |
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committer | Thomas Gleixner <tglx@linutronix.de> | 2010-02-17 18:28:05 +0100 |
commit | b7e56edba4b02f2079042c326a8cd72a44635817 (patch) | |
tree | b5042002e9747cd8fb1278d61f86d8b92a74c018 /kernel/time/timekeeping.c | |
parent | 13ca0fcaa33f6b1984c4111b6ec5df42689fea6f (diff) | |
parent | b0483e78e5c4c9871fc5541875b3bc006846d46b (diff) |
Merge branch 'linus' into x86/mm
x86/mm is on 32-rc4 and missing the spinlock namespace changes which
are needed for further commits into this topic.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel/time/timekeeping.c')
-rw-r--r-- | kernel/time/timekeeping.c | 104 |
1 files changed, 76 insertions, 28 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c index c3a4e2907ea..e2ab064c6d4 100644 --- a/kernel/time/timekeeping.c +++ b/kernel/time/timekeeping.c @@ -177,7 +177,7 @@ void timekeeping_leap_insert(int leapsecond) { xtime.tv_sec += leapsecond; wall_to_monotonic.tv_sec -= leapsecond; - update_vsyscall(&xtime, timekeeper.clock); + update_vsyscall(&xtime, timekeeper.clock, timekeeper.mult); } #ifdef CONFIG_GENERIC_TIME @@ -337,7 +337,7 @@ int do_settimeofday(struct timespec *tv) timekeeper.ntp_error = 0; ntp_clear(); - update_vsyscall(&xtime, timekeeper.clock); + update_vsyscall(&xtime, timekeeper.clock, timekeeper.mult); write_sequnlock_irqrestore(&xtime_lock, flags); @@ -488,6 +488,17 @@ int timekeeping_valid_for_hres(void) } /** + * timekeeping_max_deferment - Returns max time the clocksource can be deferred + * + * Caller must observe xtime_lock via read_seqbegin/read_seqretry to + * ensure that the clocksource does not change! + */ +u64 timekeeping_max_deferment(void) +{ + return timekeeper.clock->max_idle_ns; +} + +/** * read_persistent_clock - Return time from the persistent clock. * * Weak dummy function for arches that do not yet support it. @@ -722,6 +733,51 @@ static void timekeeping_adjust(s64 offset) timekeeper.ntp_error_shift; } + +/** + * logarithmic_accumulation - shifted accumulation of cycles + * + * This functions accumulates a shifted interval of cycles into + * into a shifted interval nanoseconds. Allows for O(log) accumulation + * loop. + * + * Returns the unconsumed cycles. + */ +static cycle_t logarithmic_accumulation(cycle_t offset, int shift) +{ + u64 nsecps = (u64)NSEC_PER_SEC << timekeeper.shift; + + /* If the offset is smaller then a shifted interval, do nothing */ + if (offset < timekeeper.cycle_interval<<shift) + return offset; + + /* Accumulate one shifted interval */ + offset -= timekeeper.cycle_interval << shift; + timekeeper.clock->cycle_last += timekeeper.cycle_interval << shift; + + timekeeper.xtime_nsec += timekeeper.xtime_interval << shift; + while (timekeeper.xtime_nsec >= nsecps) { + timekeeper.xtime_nsec -= nsecps; + xtime.tv_sec++; + second_overflow(); + } + + /* Accumulate into raw time */ + raw_time.tv_nsec += timekeeper.raw_interval << shift;; + while (raw_time.tv_nsec >= NSEC_PER_SEC) { + raw_time.tv_nsec -= NSEC_PER_SEC; + raw_time.tv_sec++; + } + + /* Accumulate error between NTP and clock interval */ + timekeeper.ntp_error += tick_length << shift; + timekeeper.ntp_error -= timekeeper.xtime_interval << + (timekeeper.ntp_error_shift + shift); + + return offset; +} + + /** * update_wall_time - Uses the current clocksource to increment the wall time * @@ -732,6 +788,7 @@ void update_wall_time(void) struct clocksource *clock; cycle_t offset; u64 nsecs; + int shift = 0, maxshift; /* Make sure we're fully resumed: */ if (unlikely(timekeeping_suspended)) @@ -745,33 +802,22 @@ void update_wall_time(void) #endif timekeeper.xtime_nsec = (s64)xtime.tv_nsec << timekeeper.shift; - /* normally this loop will run just once, however in the - * case of lost or late ticks, it will accumulate correctly. + /* + * With NO_HZ we may have to accumulate many cycle_intervals + * (think "ticks") worth of time at once. To do this efficiently, + * we calculate the largest doubling multiple of cycle_intervals + * that is smaller then the offset. We then accumulate that + * chunk in one go, and then try to consume the next smaller + * doubled multiple. */ + shift = ilog2(offset) - ilog2(timekeeper.cycle_interval); + shift = max(0, shift); + /* Bound shift to one less then what overflows tick_length */ + maxshift = (8*sizeof(tick_length) - (ilog2(tick_length)+1)) - 1; + shift = min(shift, maxshift); while (offset >= timekeeper.cycle_interval) { - u64 nsecps = (u64)NSEC_PER_SEC << timekeeper.shift; - - /* accumulate one interval */ - offset -= timekeeper.cycle_interval; - clock->cycle_last += timekeeper.cycle_interval; - - timekeeper.xtime_nsec += timekeeper.xtime_interval; - if (timekeeper.xtime_nsec >= nsecps) { - timekeeper.xtime_nsec -= nsecps; - xtime.tv_sec++; - second_overflow(); - } - - raw_time.tv_nsec += timekeeper.raw_interval; - if (raw_time.tv_nsec >= NSEC_PER_SEC) { - raw_time.tv_nsec -= NSEC_PER_SEC; - raw_time.tv_sec++; - } - - /* accumulate error between NTP and clock interval */ - timekeeper.ntp_error += tick_length; - timekeeper.ntp_error -= timekeeper.xtime_interval << - timekeeper.ntp_error_shift; + offset = logarithmic_accumulation(offset, shift); + shift--; } /* correct the clock when NTP error is too big */ @@ -811,7 +857,7 @@ void update_wall_time(void) update_xtime_cache(nsecs); /* check to see if there is a new clocksource to use */ - update_vsyscall(&xtime, timekeeper.clock); + update_vsyscall(&xtime, timekeeper.clock, timekeeper.mult); } /** @@ -834,6 +880,7 @@ void getboottime(struct timespec *ts) set_normalized_timespec(ts, -boottime.tv_sec, -boottime.tv_nsec); } +EXPORT_SYMBOL_GPL(getboottime); /** * monotonic_to_bootbased - Convert the monotonic time to boot based. @@ -843,6 +890,7 @@ void monotonic_to_bootbased(struct timespec *ts) { *ts = timespec_add_safe(*ts, total_sleep_time); } +EXPORT_SYMBOL_GPL(monotonic_to_bootbased); unsigned long get_seconds(void) { |