linux-kernel - Re: [PATCH v1 1/2] cpuidle: governors: teo: Fix tick_intercepts handling in teo

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Message-ID: <8a9482f3-d8f4-4dcf-b7eb-51a2e1bd4d3b@arm.com>
Date: Mon, 17 Nov 2025 09:06:10 +0000
From: Christian Loehle <christian.loehle@....com>
To: "Rafael J. Wysocki" <rafael@...nel.org>,
 Linux PM <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
 Aboorva Devarajan <aboorvad@...ux.ibm.com>
Subject: Re: [PATCH v1 1/2] cpuidle: governors: teo: Fix tick_intercepts
 handling in teo_update()

On 11/16/25 12:34, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> 
> The condition deciding whether or not to increase cpu_data->tick_intercepts
> in teo_update() is reverse, so fix it.
> 
> Fixes: d619b5cc6780 ("cpuidle: teo: Simplify counting events used for tick management")
> Cc: All applicable <stable@...r.kernel.org>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> 
> I'm planning to apply this for 6.19 on top of
> 
> https://lore.kernel.org/linux-pm/6228387.lOV4Wx5bFT@rafael.j.wysocki/
> 
> because that patch (indirectly) depends on commit d619b5cc6780.
> 
> ---
>  drivers/cpuidle/governors/teo.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- a/drivers/cpuidle/governors/teo.c
> +++ b/drivers/cpuidle/governors/teo.c
> @@ -251,7 +251,7 @@ static void teo_update(struct cpuidle_dr
>  		cpu_data->state_bins[idx_timer].hits += PULSE;
>  	} else {
>  		cpu_data->state_bins[idx_duration].intercepts += PULSE;
> -		if (TICK_NSEC <= measured_ns)
> +		if (measured_ns <= TICK_NSEC)

nit: Why <= instead of <?
I guess it really doesn't matter with measured_ns only being a rough approximation
with an error in the order of wakeup-latency.

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

Let me go write some tests for all these edge cases :/

IIRC Aboorva's power systems have no idle state deeper than TICK_NSEC, so
this might make a big difference here, hence CCed.