github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-05-30 10:04:04 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

time/jiffies: Inline jiffies_to_msecs() and jiffies_to_usecs()

Browse Source 
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 <edumazet@google.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260210170226.57209-1-edumazet@google.com
This commit is contained in:
Eric Dumazet 2026-02-10 17:02:25 +00:00 committed by Thomas Gleixner
parent 192c015940
commit b777b5e09e
2 changed files with 45 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

40
include/linux/jiffies.h
View File

@ -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

19
kernel/time/time.c
View File

@ -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.