Commit f6542af9 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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()
parents 61706251 b777b5e0

include/linux/jiffies.h

+38 −2
Original line number Diff line number Diff line
@@ -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

kernel/time/time.c

+7 −12
Original line number Diff line number Diff line
@@ -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

	return (HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32;

#else

	return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN;

#endif

#endif

}

EXPORT_SYMBOL(jiffies_to_usecs);

#endif



/**

 * mktime64 - Converts date to seconds.