linux-kernel - Re: [PATCH v1 2/3] cpuidle: governors: menu: Rearrange main loop in menu

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Message-ID: <bd940e70-ef2d-4382-9ea6-e2ee32cd9849@arm.com>
Date: Thu, 14 Aug 2025 14:00:33 +0100
From: Christian Loehle <christian.loehle@....com>
To: "Rafael J. Wysocki" <rafael@...nel.org>,
 Linux PM <linux-pm@...r.kernel.org>
Cc: Frederic Weisbecker <frederic@...nel.org>,
 LKML <linux-kernel@...r.kernel.org>, Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v1 2/3] cpuidle: governors: menu: Rearrange main loop in
 menu_select()

On 8/13/25 11:26, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> Reduce the indentation level in the main loop of menu_select() by
> rearranging some checks and assignments in it.
> 
> No intentional functional impact.
> 
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>


Reviewed-by: Christian Loehle <christian.loehle@....com>

> ---
>  drivers/cpuidle/governors/menu.c |   72 ++++++++++++++++++++-------------------
>  1 file changed, 37 insertions(+), 35 deletions(-)
> 
> --- a/drivers/cpuidle/governors/menu.c
> +++ b/drivers/cpuidle/governors/menu.c
> @@ -314,45 +314,47 @@
>  		if (s->exit_latency_ns > latency_req)
>  			break;
>  
> -		if (s->target_residency_ns > predicted_ns) {
> -			/*
> -			 * Use a physical idle state, not busy polling, unless
> -			 * a timer is going to trigger soon enough.
> -			 */
> -			if ((drv->states[idx].flags & CPUIDLE_FLAG_POLLING) &&
> -			    s->target_residency_ns <= data->next_timer_ns) {
> -				predicted_ns = s->target_residency_ns;
> -				idx = i;
> -				break;
> -			}
> -			if (predicted_ns < TICK_NSEC)
> -				break;
> -
> -			if (!tick_nohz_tick_stopped()) {
> -				/*
> -				 * If the state selected so far is shallow,
> -				 * waking up early won't hurt, so retain the
> -				 * tick in that case and let the governor run
> -				 * again in the next iteration of the loop.
> -				 */
> -				predicted_ns = drv->states[idx].target_residency_ns;
> -				break;
> -			}
> +		if (s->target_residency_ns <= predicted_ns) {
> +			idx = i;
> +			continue;
> +		}
> +
> +		/*
> +		 * Use a physical idle state, not busy polling, unless a timer
> +		 * is going to trigger soon enough.
> +		 */
> +		if ((drv->states[idx].flags & CPUIDLE_FLAG_POLLING) &&
> +		    s->target_residency_ns <= data->next_timer_ns) {
> +			predicted_ns = s->target_residency_ns;
> +			idx = i;
> +			break;
> +		}
>  
> +		if (predicted_ns < TICK_NSEC)
> +			break;
> +
> +		if (!tick_nohz_tick_stopped()) {
>  			/*
> -			 * If the state selected so far is shallow and this
> -			 * state's target residency matches the time till the
> -			 * closest timer event, select this one to avoid getting
> -			 * stuck in the shallow one for too long.
> +			 * If the state selected so far is shallow, waking up
> +			 * early won't hurt, so retain the tick in that case and
> +			 * let the governor run again in the next iteration of
> +			 * the idle loop.
>  			 */
> -			if (drv->states[idx].target_residency_ns < TICK_NSEC &&
> -			    s->target_residency_ns <= delta_tick)
> -				idx = i;
> -
> -			return idx;
> +			predicted_ns = drv->states[idx].target_residency_ns;
> +			break;
>  		}
>  
> -		idx = i;
> +		/*
> +		 * If the state selected so far is shallow and this state's
> +		 * target residency matches the time till the closest timer
> +		 * event, select this one to avoid getting stuck in the shallow
> +		 * one for too long.
> +		 */
> +		if (drv->states[idx].target_residency_ns < TICK_NSEC &&
> +		    s->target_residency_ns <= delta_tick)
> +			idx = i;
> +
> +		return idx;
>  	}
>  
>  	if (idx == -1)
> 
> 
>