ktime: Optimize ktime_divns for constant divisors
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>wifi-calibration
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eaa27f34e9
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8b618628b2
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@ -166,7 +166,17 @@ static inline bool ktime_before(const ktime_t cmp1, const ktime_t cmp2)
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}
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}
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#if BITS_PER_LONG < 64
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#if BITS_PER_LONG < 64
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extern u64 ktime_divns(const ktime_t kt, s64 div);
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extern u64 __ktime_divns(const ktime_t kt, s64 div);
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static inline u64 ktime_divns(const ktime_t kt, s64 div)
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{
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if (__builtin_constant_p(div) && !(div >> 32)) {
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u64 ns = kt.tv64;
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do_div(ns, div);
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return ns;
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} else {
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return __ktime_divns(kt, div);
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}
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}
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#else /* BITS_PER_LONG < 64 */
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#else /* BITS_PER_LONG < 64 */
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# define ktime_divns(kt, div) (u64)((kt).tv64 / (div))
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# define ktime_divns(kt, div) (u64)((kt).tv64 / (div))
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#endif
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#endif
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@ -266,7 +266,7 @@ lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
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/*
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/*
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* Divide a ktime value by a nanosecond value
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* Divide a ktime value by a nanosecond value
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*/
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*/
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u64 ktime_divns(const ktime_t kt, s64 div)
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u64 __ktime_divns(const ktime_t kt, s64 div)
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{
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{
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u64 dclc;
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u64 dclc;
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int sft = 0;
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int sft = 0;
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@ -282,7 +282,7 @@ u64 ktime_divns(const ktime_t kt, s64 div)
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return dclc;
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return dclc;
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}
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}
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EXPORT_SYMBOL_GPL(ktime_divns);
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EXPORT_SYMBOL_GPL(__ktime_divns);
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#endif /* BITS_PER_LONG >= 64 */
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#endif /* BITS_PER_LONG >= 64 */
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/*
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/*
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