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>

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index c3732fa74f828b61172bd8a10e2953c8226b6689..c36e1ea7ef082118fcf4a7f076bffb8b151f6aca 100644 (file)
--- 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.