Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH] optimize ktime_divns for constant divisors | Date | Wed, 03 Dec 2014 21:03:48 +0100 |
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On Wednesday 03 December 2014 14:43:06 Nicolas Pitre wrote: > 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. > > Signed-off-by: Nicolas Pitre <nico@linaro.org>
Very cool. I've been thinking about doing something similar for the general case but couldn't get the math to work.
Can you think of an architecture-independent way to ktime_to_sec, ktime_to_ms, and ktime_to_us efficiently based on what you did for the ARM do_div implementation?
Arnd
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