diff options
| author | Linus Torvalds <torvalds@linux-foundation.org> | 2026-03-01 12:15:58 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2026-03-01 12:15:58 -0800 |
| commit | f6542af92298d8a44ab5588144086fa2d0edf391 (patch) | |
| tree | c577fe82f6e3b882649c5244e3777e064bec016b | |
| parent | 61706251492eff650e91c58507bc77e1a12c7fbb (diff) | |
| parent | b777b5e09eabeefc6ba80f4296366a4742701103 (diff) | |
Merge tag 'timers-urgent-2026-03-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer fix from Ingo Molnar:
"Improve the inlining of jiffies_to_msecs() and jiffies_to_usecs(), for
the common HZ=100, 250 or 1000 cases. Only use a function call for odd
HZ values like HZ=300 that generate more code.
The function call overhead showed up in performance tests of the TCP
code"
* tag 'timers-urgent-2026-03-01' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
time/jiffies: Inline jiffies_to_msecs() and jiffies_to_usecs()
| -rw-r--r-- | include/linux/jiffies.h | 40 | ||||
| -rw-r--r-- | kernel/time/time.c | 19 |
2 files changed, 45 insertions, 14 deletions
diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h index fdef2c155c27..d1c3d4941854 100644 --- a/include/linux/jiffies.h +++ b/include/linux/jiffies.h @@ -434,8 +434,44 @@ extern unsigned long preset_lpj; /* * Convert various time units to each other: */ -extern unsigned int jiffies_to_msecs(const unsigned long j); -extern unsigned int jiffies_to_usecs(const unsigned long j); + +#if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ) +/** + * jiffies_to_msecs - Convert jiffies to milliseconds + * @j: jiffies value + * + * This inline version takes care of HZ in {100,250,1000}. + * + * Return: milliseconds value + */ +static inline unsigned int jiffies_to_msecs(const unsigned long j) +{ + return (MSEC_PER_SEC / HZ) * j; +} +#else +unsigned int jiffies_to_msecs(const unsigned long j); +#endif + +#if !(USEC_PER_SEC % HZ) +/** + * jiffies_to_usecs - Convert jiffies to microseconds + * @j: jiffies value + * + * Return: microseconds value + */ +static inline unsigned int jiffies_to_usecs(const unsigned long j) +{ + /* + * Hz usually doesn't go much further MSEC_PER_SEC. + * jiffies_to_usecs() and usecs_to_jiffies() depend on that. + */ + BUILD_BUG_ON(HZ > USEC_PER_SEC); + + return (USEC_PER_SEC / HZ) * j; +} +#else +unsigned int jiffies_to_usecs(const unsigned long j); +#endif /** * jiffies_to_nsecs - Convert jiffies to nanoseconds diff --git a/kernel/time/time.c b/kernel/time/time.c index 0ba8e3c50d62..36fd2313ae7e 100644 --- a/kernel/time/time.c +++ b/kernel/time/time.c @@ -365,20 +365,16 @@ SYSCALL_DEFINE1(adjtimex_time32, struct old_timex32 __user *, utp) } #endif +#if HZ > MSEC_PER_SEC || (MSEC_PER_SEC % HZ) /** * jiffies_to_msecs - Convert jiffies to milliseconds * @j: jiffies value * - * Avoid unnecessary multiplications/divisions in the - * two most common HZ cases. - * * Return: milliseconds value */ 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) +#if HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC) return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC); #else # if BITS_PER_LONG == 32 @@ -390,7 +386,9 @@ unsigned int jiffies_to_msecs(const unsigned long j) #endif } EXPORT_SYMBOL(jiffies_to_msecs); +#endif +#if (USEC_PER_SEC % HZ) /** * jiffies_to_usecs - Convert jiffies to microseconds * @j: jiffies value @@ -405,17 +403,14 @@ unsigned int jiffies_to_usecs(const unsigned long j) */ BUILD_BUG_ON(HZ > USEC_PER_SEC); -#if !(USEC_PER_SEC % HZ) - return (USEC_PER_SEC / HZ) * j; -#else -# if BITS_PER_LONG == 32 +#if BITS_PER_LONG == 32 return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32; -# else +#else return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN; -# endif #endif } EXPORT_SYMBOL(jiffies_to_usecs); +#endif /** * mktime64 - Converts date to seconds. |