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

Liu Song
2024-02-27T07:48:33Z

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@linutronix.de>
> Signed-off-by: Bitao Hu <yaoma@linux.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@linux.alibaba.com> |

||