cpuidle: menu: help gcc generate slightly better code
We know that the avg variable actually ends up holding a 32 bit
quantity, since it's an average of such numbers. It is only a u64
because it is temporarily used to hold the sum. Making it an actual
u32 allows gcc to generate slightly better code, e.g. when computing
the square, it can do a 32x32->64 multiply.
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
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 beef7ae..27fc733 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -199,8 +199,8 @@
static void get_typical_interval(struct menu_device *data)
{
int i, divisor;
- unsigned int max, thresh;
- uint64_t avg, variance;
+ unsigned int max, thresh, avg;
+ uint64_t sum, variance;
thresh = UINT_MAX; /* Discard outliers above this value */
@@ -208,28 +208,28 @@
/* First calculate the average of past intervals */
max = 0;
- avg = 0;
+ sum = 0;
divisor = 0;
for (i = 0; i < INTERVALS; i++) {
unsigned int value = data->intervals[i];
if (value <= thresh) {
- avg += value;
+ sum += value;
divisor++;
if (value > max)
max = value;
}
}
if (divisor == INTERVALS)
- avg >>= INTERVAL_SHIFT;
+ avg = sum >> INTERVAL_SHIFT;
else
- do_div(avg, divisor);
+ avg = div_u64(sum, divisor);
/* Then try to determine variance */
variance = 0;
for (i = 0; i < INTERVALS; i++) {
unsigned int value = data->intervals[i];
if (value <= thresh) {
- int64_t diff = value - avg;
+ int64_t diff = (int64_t)value - avg;
variance += diff * diff;
}
}
@@ -251,7 +251,7 @@
* Use this result only if there is no timer to wake us up sooner.
*/
if (likely(variance <= U64_MAX/36)) {
- if (((avg*avg > variance*36) && (divisor * 4 >= INTERVALS * 3))
+ if ((((u64)avg*avg > variance*36) && (divisor * 4 >= INTERVALS * 3))
|| variance <= 400) {
if (data->next_timer_us > avg)
data->predicted_us = avg;
