From: Nicolas Pitre <nicolas.pitre@linaro.org>
Date: Wed, 3 Dec 2014 19:43:06 +0000 (-0500)
Subject: ktime: Optimize ktime_divns for constant divisors
X-Git-Tag: omap-for-v4.1/prcm-dts-mfd-syscon-fix~162^2~1^2~7
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8b618628b2bf83512fc8df5e8672619d65adfdfb;p=pandora-kernel.git

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>
---

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