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| author | Nicolas Pitre <nicolas.pitre@linaro.org> | 2014-12-03 14:43:06 -0500 |
|---|---|---|
| committer | Sasha Levin <sasha.levin@oracle.com> | 2015-06-09 13:43:49 -0400 |
| commit | 55fe6e07b589b0d11bced3ac1d74829b416e7fc6 (patch) | |
| tree | 008d8f1648f2260d6faa50df0952dec7820cbbc4 /kernel | |
| parent | 08a468bf87293f0d18f7ce8ad66a42f4371395f7 (diff) | |
| download | lwn-55fe6e07b589b0d11bced3ac1d74829b416e7fc6.tar.gz lwn-55fe6e07b589b0d11bced3ac1d74829b416e7fc6.zip | |
ktime: Optimize ktime_divns for constant divisors
[ Upstream commit 8b618628b2bf83512fc8df5e8672619d65adfdfb ]
At least on ARM, do_div() is optimized to turn constant divisors into
an inline multiplication by the reciprocal value at compile time.
However this optimization is missed entirely whenever ktime_divns() is
used and the slow out-of-line division code is used all the time.
Let ktime_divns() use do_div() inline whenever the divisor is constant
and small enough. This will make things like ktime_to_us() and
ktime_to_ms() much faster.
Cc: Arnd Bergmann <arnd.bergmann@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Nicolas Pitre <nico@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/time/hrtimer.c | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c index d8c724cda37b..5e4d51c2f85a 100644 --- a/kernel/time/hrtimer.c +++ b/kernel/time/hrtimer.c @@ -266,7 +266,7 @@ lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags) /* * Divide a ktime value by a nanosecond value */ -u64 ktime_divns(const ktime_t kt, s64 div) +u64 __ktime_divns(const ktime_t kt, s64 div) { u64 dclc; int sft = 0; @@ -282,7 +282,7 @@ u64 ktime_divns(const ktime_t kt, s64 div) return dclc; } -EXPORT_SYMBOL_GPL(ktime_divns); +EXPORT_SYMBOL_GPL(__ktime_divns); #endif /* BITS_PER_LONG >= 64 */ /* |