Commit 320eee77 authored by venkatesh.pallipadi@intel.com's avatar venkatesh.pallipadi@intel.com Committed by Andi Kleen
Browse files

cpuidle: Menu governor fix wrong usage of measured_us 



There is a bug in menu governor where we have
		if (data->elapsed_us < data->elapsed_us + measured_us)

with measured_us already having elapsed_us added in tickless case here
	unsigned int measured_us =
		cpuidle_get_last_residency(dev) + data->elapsed_us;

Also, it should be last_residency, not measured_us, that need to be used to
do comparing and distinguish between expected & non-expected events.

Refactor menu_reflect() to fix these two problems.

Signed-off-by: default avatarVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: default avatarWei Gang <gang.wei@intel.com>
Signed-off-by: default avatarAndi Kleen <ak@linux.intel.com>
parent a2bd9202

drivers/cpuidle/governors/menu.c

+19 −12
Original line number Diff line number Diff line
@@ -74,9 +74,9 @@ static void menu_reflect(struct cpuidle_device *dev) 
{

	struct menu_device *data = &__get_cpu_var(menu_devices);

	int last_idx = data->last_state_idx;

	unsigned int measured_us =

		cpuidle_get_last_residency(dev) + data->elapsed_us;

	unsigned int last_idle_us = cpuidle_get_last_residency(dev);

	struct cpuidle_state *target = &dev->states[last_idx];

	unsigned int measured_us;



	/*

	 * Ugh, this idle state doesn't support residency measurements, so we
@@ -84,20 +84,27 @@ static void menu_reflect(struct cpuidle_device *dev) 
	 * for one full standard timer tick.  However, be aware that this

	 * could potentially result in a suboptimal state transition.

	 */

	if (!(target->flags & CPUIDLE_FLAG_TIME_VALID))

		measured_us = USEC_PER_SEC / HZ;

	if (unlikely(!(target->flags & CPUIDLE_FLAG_TIME_VALID)))

		last_idle_us = USEC_PER_SEC / HZ;



	/* Predict time remaining until next break event */

	if (measured_us + BREAK_FUZZ < data->expected_us - target->exit_latency) {

	/*

	 * measured_us and elapsed_us are the cumulative idle time, since the

	 * last time we were woken out of idle by an interrupt.

	 */

	if (data->elapsed_us <= data->elapsed_us + last_idle_us)

		measured_us = data->elapsed_us + last_idle_us;

	else

		measured_us = -1;



	/* Predict time until next break event */

	data->predicted_us = max(measured_us, data->last_measured_us);



	if (last_idle_us + BREAK_FUZZ <

	    data->expected_us - target->exit_latency) {

		data->last_measured_us = measured_us;

		data->elapsed_us = 0;

	} else {

		if (data->elapsed_us < data->elapsed_us + measured_us)

		data->elapsed_us = measured_us;

		else

			data->elapsed_us = -1;

		data->predicted_us = max(measured_us, data->last_measured_us);

	}

}

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