linux-kernel - Re: [PATCHv10 3/4] genirq: Avoid summation loops for /proc/interrupts

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Message-ID: <2c1d0ece-a781-4bf7-89dd-cea428842d05@linux.alibaba.com>
Date: Tue, 27 Feb 2024 15:48:27 +0800
From: Liu Song <liusong@...ux.alibaba.com>
To: Bitao Hu <yaoma@...ux.alibaba.com>, dianders@...omium.org,
 tglx@...utronix.de, akpm@...ux-foundation.org, pmladek@...e.com,
 kernelfans@...il.com, deller@....de, npiggin@...il.com,
 tsbogend@...ha.franken.de, James.Bottomley@...senPartnership.com,
 jan.kiszka@...mens.com
Cc: linux-kernel@...r.kernel.org, linux-mips@...r.kernel.org,
 linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCHv10 3/4] genirq: Avoid summation loops for /proc/interrupts


在 2024/2/26 10:09, Bitao Hu 写道:
> We could use the irq_desc::tot_count member to avoid the summation
> loop for interrupts which are not marked as 'PER_CPU' interrupts in
> 'show_interrupts'. This could reduce the time overhead of reading
> /proc/interrupts.
>
> Originally-by: Thomas Gleixner <tglx@...utronix.de>
> Signed-off-by: Bitao Hu <yaoma@...ux.alibaba.com>
> ---
>   include/linux/irqdesc.h | 2 ++
>   kernel/irq/irqdesc.c    | 2 +-
>   kernel/irq/proc.c       | 9 +++++++--
>   3 files changed, 10 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h
> index 2912b1998670..1ee96d7232b4 100644
> --- a/include/linux/irqdesc.h
> +++ b/include/linux/irqdesc.h
> @@ -121,6 +121,8 @@ static inline void irq_unlock_sparse(void) { }
>   extern struct irq_desc irq_desc[NR_IRQS];
>   #endif
>   
> +extern bool irq_is_nmi(struct irq_desc *desc);
> +
>   static inline unsigned int irq_desc_kstat_cpu(struct irq_desc *desc,
>   					      unsigned int cpu)
>   {
> diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
> index 9cd17080b2d8..56a767957a9d 100644
> --- a/kernel/irq/irqdesc.c
> +++ b/kernel/irq/irqdesc.c
> @@ -955,7 +955,7 @@ unsigned int kstat_irqs_cpu(unsigned int irq, int cpu)
>   	return desc && desc->kstat_irqs ? per_cpu(desc->kstat_irqs->cnt, cpu) : 0;
>   }
>   
> -static bool irq_is_nmi(struct irq_desc *desc)
> +bool irq_is_nmi(struct irq_desc *desc)
>   {
>   	return desc->istate & IRQS_NMI;
>   }
> diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c
> index 6954e0a02047..b3b1b93f0410 100644
> --- a/kernel/irq/proc.c
> +++ b/kernel/irq/proc.c
> @@ -489,8 +489,13 @@ int show_interrupts(struct seq_file *p, void *v)
>   		goto outsparse;
>   
>   	if (desc->kstat_irqs) {
> -		for_each_online_cpu(j)
> -			any_count |= data_race(per_cpu(desc->kstat_irqs->cnt, j));
> +		if (!irq_settings_is_per_cpu_devid(desc) &&
> +		    !irq_settings_is_per_cpu(desc) &&
> +		    !irq_is_nmi(desc))
> +			any_count = data_race(desc->tot_count);
> +		else
> +			for_each_online_cpu(j)
> +				any_count |= data_race(per_cpu(desc->kstat_irqs->cnt, j));
>   	}
>   
>   	if ((!desc->action || irq_desc_is_chained(desc)) && !any_count)

The modification borrows from the implementation of |kstat_irqs. Looks 
good.|

|Reviewed-by: Liu Song <liusong@...ux.alibaba.com> |

||