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Commit 3b99669b authored by Rasmus Villemoes's avatar Rasmus Villemoes Committed by Rafael J. Wysocki
Browse files

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: default avatarRasmus Villemoes <linux@rasmusvillemoes.dk>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 7024b18c

drivers/cpuidle/governors/menu.c

+8 −8
Original line number Diff line number Diff line
@@ -199,8 +199,8 @@ static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev); 
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 @@ static void get_typical_interval(struct menu_device *data) 


	/* 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 @@ static void get_typical_interval(struct menu_device *data) 
	 * 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;