From b777b5e09eabeefc6ba80f4296366a4742701103 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Tue, 10 Feb 2026 17:02:25 +0000 Subject: time/jiffies: Inline jiffies_to_msecs() and jiffies_to_usecs() For common cases (HZ=100, 250 or 1000), these helpers are at most one multiply, so there is no point calling a tiny function. Keep them out of line for HZ=300 and others. This saves cycles in TCP fast path, among other things. $ scripts/bloat-o-meter -t vmlinux.old vmlinux.new add/remove: 0/8 grow/shrink: 25/89 up/down: 530/-3474 (-2944) ... nla_put_msecs 193 - -193 message_stats_print 2131 920 -1211 Total: Before=25365208, After=25362264, chg -0.01% Signed-off-by: Eric Dumazet Signed-off-by: Thomas Gleixner Link: https://patch.msgid.link/20260210170226.57209-1-edumazet@google.com --- include/linux/jiffies.h | 40 ++++++++++++++++++++++++++++++++++++++-- 1 file changed, 38 insertions(+), 2 deletions(-) (limited to 'include/linux') 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 -- cgit v1.2.3