From ae77930060338226a4377d3b93580c43b5ec82ae Mon Sep 17 00:00:00 2001 From: Mel Gorman Date: Wed, 6 Aug 2014 14:19:18 +0100 Subject: [PATCH] cpuidle: menu: Use shifts when calculating averages where possible We use do_div even though the divisor will usually be a power-of-two unless there are unusual outliers. Use shifts where possible Signed-off-by: Mel Gorman Signed-off-by: Rafael J. Wysocki --- drivers/cpuidle/governors/menu.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c index c3732fa74f82..c36e1ea7ef08 100644 --- a/drivers/cpuidle/governors/menu.c +++ b/drivers/cpuidle/governors/menu.c @@ -31,7 +31,8 @@ * The default values do not overflow. */ #define BUCKETS 12 -#define INTERVALS 8 +#define INTERVAL_SHIFT 3 +#define INTERVALS (1UL << INTERVAL_SHIFT) #define RESOLUTION 1024 #define DECAY 8 #define MAX_INTERESTING 50000 @@ -227,7 +228,10 @@ again: max = value; } } - do_div(avg, divisor); + if (divisor == INTERVALS) + avg >>= INTERVAL_SHIFT; + else + do_div(avg, divisor); /* Then try to determine standard deviation */ stddev = 0; @@ -238,7 +242,11 @@ again: stddev += diff * diff; } } - do_div(stddev, divisor); + if (divisor == INTERVALS) + stddev >>= INTERVAL_SHIFT; + else + do_div(stddev, divisor); + /* * The typical interval is obtained when standard deviation is small * or standard deviation is small compared to the average interval. -- 2.34.1