linux-kernel - Re: [PATCH 2/7] Cpuidle: Use actual state latency in menu governor

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Date:	Mon, 24 Feb 2014 23:35:40 +0100
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Tuukka Tikkanen <tuukka.tikkanen@...aro.org>,
	linux-pm@...r.kernel.org, rjw@...ysocki.net
CC:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/7] Cpuidle: Use actual state latency in menu governor

On 02/24/2014 07:29 AM, Tuukka Tikkanen wrote:
> Currently menu governor records the exit latency of the state it has
> chosen for the idle period. The stored latency value is then later
> used to calculate the actual length of the idle period. This value
> may however be incorrect, as the entered state may not be the one
> chosen by the governor. The entered state information is available,
> so we can use that to obtain the real exit latency.
>
> Signed-off-by: Tuukka Tikkanen <tuukka.tikkanen@...aro.org>

Acked-by: Daniel Lezcano <daniel.lezcano@...aro.org>

> ---
>   drivers/cpuidle/governors/menu.c |    7 ++-----
>   1 file changed, 2 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
> index e9a2a27..115386a 100644
> --- a/drivers/cpuidle/governors/menu.c
> +++ b/drivers/cpuidle/governors/menu.c
> @@ -124,7 +124,6 @@ struct menu_device {
>
>   	unsigned int	next_timer_us;
>   	unsigned int	predicted_us;
> -	unsigned int	exit_us;
>   	unsigned int	bucket;
>   	unsigned int	correction_factor[BUCKETS];
>   	unsigned int	intervals[INTERVALS];
> @@ -298,7 +297,6 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
>   	}
>
>   	data->last_state_idx = 0;
> -	data->exit_us = 0;
>
>   	/* Special case when user has set very strict latency requirement */
>   	if (unlikely(latency_req == 0))
> @@ -359,7 +357,6 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev)
>   			continue;
>
>   		data->last_state_idx = i;
> -		data->exit_us = s->exit_latency;
>   	}
>
>   	return data->last_state_idx;
> @@ -410,8 +407,8 @@ static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev)
>   	 * We correct for the exit latency; we are assuming here that the
>   	 * exit latency happens after the event that we're interested in.
>   	 */
> -	if (measured_us > data->exit_us)
> -		measured_us -= data->exit_us;
> +	if (measured_us > target->exit_latency)
> +		measured_us -= target->exit_latency;
>
>
>   	/* Update our correction ratio */
>


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