linux-kernel - Re: [PATCH 1/1] cpuidle/menu: avoid prioritizing physical state over polling state

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Message-ID: <c20a07e4-b9e6-4a66-80f5-63d679b17c3b@arm.com>
Date: Tue, 13 Aug 2024 14:09:20 +0100
From: Christian Loehle <christian.loehle@....com>
To: Aboorva Devarajan <aboorvad@...ux.ibm.com>, rafael@...nel.org,
 daniel.lezcano@...aro.org, linux-pm@...r.kernel.org,
 linux-kernel@...r.kernel.org
Cc: gautam@...ux.ibm.com
Subject: Re: [PATCH 1/1] cpuidle/menu: avoid prioritizing physical state over
 polling state

On 8/9/24 08:31, Aboorva Devarajan wrote:
> Update the cpuidle menu governor to avoid prioritizing physical states
> over polling states when predicted idle duration is lesser than the
> physical states target residency duration for performance gains.
> 
> Signed-off-by: Aboorva Devarajan <aboorvad@...ux.ibm.com>
> ---
>  drivers/cpuidle/governors/menu.c | 11 -----------
>  1 file changed, 11 deletions(-)
> 
> diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
> index f3c9d49f0f2a..cf99ca103f9b 100644
> --- a/drivers/cpuidle/governors/menu.c
> +++ b/drivers/cpuidle/governors/menu.c
> @@ -354,17 +354,6 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
>  			idx = i; /* first enabled state */
>  
>  		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->exit_latency_ns <= latency_req &&
> -			    s->target_residency_ns <= data->next_timer_ns) {
> -				predicted_ns = s->target_residency_ns;
> -				idx = i;
> -				break;
> -			}
>  			if (predicted_ns < TICK_NSEC)
>  				break;
>  


How about this?
data->next_timer_ns is set to KTIME_MAX in case the last few intervals were
very short, which might be the case for you.

-->8--

diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c
index f3c9d49f0f2a..77b40201c446 100644
--- a/drivers/cpuidle/governors/menu.c
+++ b/drivers/cpuidle/governors/menu.c
@@ -360,6 +360,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
                         */
                        if ((drv->states[idx].flags & CPUIDLE_FLAG_POLLING) &&
                            s->exit_latency_ns <= latency_req &&
+                           data->next_timer_ns != KTIME_MAX &&
                            s->target_residency_ns <= data->next_timer_ns) {
                                predicted_ns = s->target_residency_ns;
                                idx = i;