Commit b777b5e0 authored by Eric Dumazet's avatar Eric Dumazet Committed by Thomas Gleixner
Browse files

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: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarThomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260210170226.57209-1-edumazet@google.com
parent 192c0159

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.