linux-kernel - Re: [PATCH 4/6] genirq: optimize irq_do_set

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Date: Tue, 14 May 2024 20:51:39 +0800
From: Jinjie Ruan <ruanjinjie@...wei.com>
To: Yury Norov <yury.norov@...il.com>, <linux-kernel@...r.kernel.org>, Greg
 Kroah-Hartman <gregkh@...uxfoundation.org>, "Paul E. McKenney"
	<paulmck@...nel.org>, "Rafael J. Wysocki" <rafael@...nel.org>, Anna-Maria
 Behnsen <anna-maria@...utronix.de>, Ben Segall <bsegall@...gle.com>, Daniel
 Bristot de Oliveira <bristot@...hat.com>, Dietmar Eggemann
	<dietmar.eggemann@....com>, Frederic Weisbecker <frederic@...nel.org>, Imran
 Khan <imran.f.khan@...cle.com>, Ingo Molnar <mingo@...hat.com>, Johannes
 Weiner <hannes@...xchg.org>, Juri Lelli <juri.lelli@...hat.com>, Leonardo
 Bras <leobras@...hat.com>, Mel Gorman <mgorman@...e.de>, Peter Zijlstra
	<peterz@...radead.org>, Rik van Riel <riel@...riel.com>, Steven Rostedt
	<rostedt@...dmis.org>, Tejun Heo <tj@...nel.org>, Thomas Gleixner
	<tglx@...utronix.de>, Valentin Schneider <vschneid@...hat.com>, Vincent
 Guittot <vincent.guittot@...aro.org>, Waiman Long <longman@...hat.com>, Zefan
 Li <lizefan.x@...edance.com>, <cgroups@...r.kernel.org>
Subject: Re: [PATCH 4/6] genirq: optimize irq_do_set_affinity()



On 2024/5/14 6:01, Yury Norov wrote:
> If mask == desc->irq_common_data.affinity, copying one to another is
> useless, and we can just skip it.
> 
> Signed-off-by: Yury Norov <yury.norov@...il.com>
> ---
>  kernel/irq/manage.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
> index bf9ae8a8686f..ad9ed9fdf919 100644
> --- a/kernel/irq/manage.c
> +++ b/kernel/irq/manage.c
> @@ -285,7 +285,8 @@ int irq_do_set_affinity(struct irq_data *data, const struct cpumask *mask,
>  	switch (ret) {
>  	case IRQ_SET_MASK_OK:
>  	case IRQ_SET_MASK_OK_DONE:
> -		cpumask_copy(desc->irq_common_data.affinity, mask);
> +		if (desc->irq_common_data.affinity != mask)
> +			cpumask_copy(desc->irq_common_data.affinity, mask);

It seems that mask is a pointer, shouldn't use "cpumask_equal"？

>  		fallthrough;
>  	case IRQ_SET_MASK_OK_NOCOPY:
>  		irq_validate_effective_affinity(data);