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 <mgorman@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files 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.