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cpuidle: menu: Use shifts when calculating averages where possible

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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 <mgorman@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Mel Gorman 2014-08-06 14:19:18 +01:00 committed by Rafael J. Wysocki
parent dd38c9d35b
commit ae77930060
1 changed files with 11 additions and 3 deletions
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14
drivers/cpuidle/governors/menu.c
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@ -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.