diff options
Diffstat (limited to 'kernel/time.c')
| -rw-r--r-- | kernel/time.c | 213 |
1 files changed, 213 insertions, 0 deletions
diff --git a/kernel/time.c b/kernel/time.c index 0e017bff4c1..4a865717158 100644 --- a/kernel/time.c +++ b/kernel/time.c @@ -470,6 +470,219 @@ struct timeval ns_to_timeval(const s64 nsec) return tv; } +/* + * Convert jiffies to milliseconds and back. + * + * Avoid unnecessary multiplications/divisions in the + * two most common HZ cases: + */ +unsigned int jiffies_to_msecs(const unsigned long j) +{ +#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ) + return (MSEC_PER_SEC / HZ) * j; +#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC) + return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC); +#else + return (j * MSEC_PER_SEC) / HZ; +#endif +} +EXPORT_SYMBOL(jiffies_to_msecs); + +unsigned int jiffies_to_usecs(const unsigned long j) +{ +#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ) + return (USEC_PER_SEC / HZ) * j; +#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC) + return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC); +#else + return (j * USEC_PER_SEC) / HZ; +#endif +} +EXPORT_SYMBOL(jiffies_to_usecs); + +unsigned long msecs_to_jiffies(const unsigned int m) +{ + if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET)) + return MAX_JIFFY_OFFSET; +#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ) + return (m + (MSEC_PER_SEC / HZ) - 1) / (MSEC_PER_SEC / HZ); +#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC) + return m * (HZ / MSEC_PER_SEC); +#else + return (m * HZ + MSEC_PER_SEC - 1) / MSEC_PER_SEC; +#endif +} +EXPORT_SYMBOL(msecs_to_jiffies); + +unsigned long usecs_to_jiffies(const unsigned int u) +{ + if (u > jiffies_to_usecs(MAX_JIFFY_OFFSET)) + return MAX_JIFFY_OFFSET; +#if HZ <= USEC_PER_SEC && !(USEC_PER_SEC % HZ) + return (u + (USEC_PER_SEC / HZ) - 1) / (USEC_PER_SEC / HZ); +#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC) + return u * (HZ / USEC_PER_SEC); +#else + return (u * HZ + USEC_PER_SEC - 1) / USEC_PER_SEC; +#endif +} +EXPORT_SYMBOL(usecs_to_jiffies); + +/* + * The TICK_NSEC - 1 rounds up the value to the next resolution. Note + * that a remainder subtract here would not do the right thing as the + * resolution values don't fall on second boundries. I.e. the line: + * nsec -= nsec % TICK_NSEC; is NOT a correct resolution rounding. + * + * Rather, we just shift the bits off the right. + * + * The >> (NSEC_JIFFIE_SC - SEC_JIFFIE_SC) converts the scaled nsec + * value to a scaled second value. + */ +unsigned long +timespec_to_jiffies(const struct timespec *value) +{ + unsigned long sec = value->tv_sec; + long nsec = value->tv_nsec + TICK_NSEC - 1; + + if (sec >= MAX_SEC_IN_JIFFIES){ + sec = MAX_SEC_IN_JIFFIES; + nsec = 0; + } + return (((u64)sec * SEC_CONVERSION) + + (((u64)nsec * NSEC_CONVERSION) >> + (NSEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC; + +} +EXPORT_SYMBOL(timespec_to_jiffies); + +void +jiffies_to_timespec(const unsigned long jiffies, struct timespec *value) +{ + /* + * Convert jiffies to nanoseconds and separate with + * one divide. + */ + u64 nsec = (u64)jiffies * TICK_NSEC; + value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &value->tv_nsec); +} +EXPORT_SYMBOL(jiffies_to_timespec); + +/* Same for "timeval" + * + * Well, almost. The problem here is that the real system resolution is + * in nanoseconds and the value being converted is in micro seconds. + * Also for some machines (those that use HZ = 1024, in-particular), + * there is a LARGE error in the tick size in microseconds. + + * The solution we use is to do the rounding AFTER we convert the + * microsecond part. Thus the USEC_ROUND, the bits to be shifted off. + * Instruction wise, this should cost only an additional add with carry + * instruction above the way it was done above. + */ +unsigned long +timeval_to_jiffies(const struct timeval *value) +{ + unsigned long sec = value->tv_sec; + long usec = value->tv_usec; + + if (sec >= MAX_SEC_IN_JIFFIES){ + sec = MAX_SEC_IN_JIFFIES; + usec = 0; + } + return (((u64)sec * SEC_CONVERSION) + + (((u64)usec * USEC_CONVERSION + USEC_ROUND) >> + (USEC_JIFFIE_SC - SEC_JIFFIE_SC))) >> SEC_JIFFIE_SC; +} + +void jiffies_to_timeval(const unsigned long jiffies, struct timeval *value) +{ + /* + * Convert jiffies to nanoseconds and separate with + * one divide. + */ + u64 nsec = (u64)jiffies * TICK_NSEC; + long tv_usec; + + value->tv_sec = div_long_long_rem(nsec, NSEC_PER_SEC, &tv_usec); + tv_usec /= NSEC_PER_USEC; + value->tv_usec = tv_usec; +} + +/* + * Convert jiffies/jiffies_64 to clock_t and back. + */ +clock_t jiffies_to_clock_t(long x) +{ +#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0 + return x / (HZ / USER_HZ); +#else + u64 tmp = (u64)x * TICK_NSEC; + do_div(tmp, (NSEC_PER_SEC / USER_HZ)); + return (long)tmp; +#endif +} +EXPORT_SYMBOL(jiffies_to_clock_t); + +unsigned long clock_t_to_jiffies(unsigned long x) +{ +#if (HZ % USER_HZ)==0 + if (x >= ~0UL / (HZ / USER_HZ)) + return ~0UL; + return x * (HZ / USER_HZ); +#else + u64 jif; + + /* Don't worry about loss of precision here .. */ + if (x >= ~0UL / HZ * USER_HZ) + return ~0UL; + + /* .. but do try to contain it here */ + jif = x * (u64) HZ; + do_div(jif, USER_HZ); + return jif; +#endif +} +EXPORT_SYMBOL(clock_t_to_jiffies); + +u64 jiffies_64_to_clock_t(u64 x) +{ +#if (TICK_NSEC % (NSEC_PER_SEC / USER_HZ)) == 0 + do_div(x, HZ / USER_HZ); +#else + /* + * There are better ways that don't overflow early, + * but even this doesn't overflow in hundreds of years + * in 64 bits, so.. + */ + x *= TICK_NSEC; + do_div(x, (NSEC_PER_SEC / USER_HZ)); +#endif + return x; +} + +EXPORT_SYMBOL(jiffies_64_to_clock_t); + +u64 nsec_to_clock_t(u64 x) +{ +#if (NSEC_PER_SEC % USER_HZ) == 0 + do_div(x, (NSEC_PER_SEC / USER_HZ)); +#elif (USER_HZ % 512) == 0 + x *= USER_HZ/512; + do_div(x, (NSEC_PER_SEC / 512)); +#else + /* + * max relative error 5.7e-8 (1.8s per year) for USER_HZ <= 1024, + * overflow after 64.99 years. + * exact for HZ=60, 72, 90, 120, 144, 180, 300, 600, 900, ... + */ + x *= 9; + do_div(x, (unsigned long)((9ull * NSEC_PER_SEC + (USER_HZ/2)) / + USER_HZ)); +#endif + return x; +} + #if (BITS_PER_LONG < 64) u64 get_jiffies_64(void) { |