Commit 25a4a015 authored by Bitao Hu's avatar Bitao Hu Committed by Thomas Gleixner
Browse files

genirq: Avoid summation loops for /proc/interrupts 



show_interrupts() unconditionally accumulates the per CPU interrupt
statistics to determine whether an interrupt was ever raised.

This can be avoided for all interrupts which are not strictly per CPU
and not of type NMI because those interrupts provide already an
accumulated counter. The required logic is already implemented in
kstat_irqs().

Split the inner access logic out of kstat_irqs() and use it for
kstat_irqs() and show_interrupts() to avoid the accumulation loop
when possible.

Originally-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarBitao Hu <yaoma@linux.alibaba.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarLiu Song <liusong@linux.alibaba.com>
Reviewed-by: default avatarDouglas Anderson <dianders@chromium.org>
Link: https://lore.kernel.org/r/20240411074134.30922-4-yaoma@linux.alibaba.com
parent 99cf63c5

kernel/irq/internals.h

+2 −0
Original line number Diff line number Diff line
@@ -98,6 +98,8 @@ extern void mask_irq(struct irq_desc *desc); 
extern void unmask_irq(struct irq_desc *desc);

extern void unmask_threaded_irq(struct irq_desc *desc);



extern unsigned int kstat_irqs_desc(struct irq_desc *desc, const struct cpumask *cpumask);



#ifdef CONFIG_SPARSE_IRQ

static inline void irq_mark_irq(unsigned int irq) { }

#else

kernel/irq/irqdesc.c

+11 −5
Original line number Diff line number Diff line
@@ -976,24 +976,30 @@ static bool irq_is_nmi(struct irq_desc *desc) 
	return desc->istate & IRQS_NMI;

}



static unsigned int kstat_irqs(unsigned int irq)

unsigned int kstat_irqs_desc(struct irq_desc *desc, const struct cpumask *cpumask)

{

	struct irq_desc *desc = irq_to_desc(irq);

	unsigned int sum = 0;

	int cpu;



	if (!desc || !desc->kstat_irqs)

		return 0;

	if (!irq_settings_is_per_cpu_devid(desc) &&

	    !irq_settings_is_per_cpu(desc) &&

	    !irq_is_nmi(desc))

		return data_race(desc->tot_count);



	for_each_possible_cpu(cpu)

	for_each_cpu(cpu, cpumask)

		sum += data_race(per_cpu(desc->kstat_irqs->cnt, cpu));

	return sum;

}



static unsigned int kstat_irqs(unsigned int irq)

{

	struct irq_desc *desc = irq_to_desc(irq);



	if (!desc || !desc->kstat_irqs)

		return 0;

	return kstat_irqs_desc(desc, cpu_possible_mask);

}



#ifdef CONFIG_GENERIC_IRQ_STAT_SNAPSHOT



void kstat_snapshot_irqs(void)

kernel/irq/proc.c

+2 −4
Original line number Diff line number Diff line
@@ -488,10 +488,8 @@ int show_interrupts(struct seq_file *p, void *v) 
	if (!desc || irq_settings_is_hidden(desc))

		goto outsparse;



	if (desc->kstat_irqs) {

		for_each_online_cpu(j)

			any_count |= data_race(per_cpu(desc->kstat_irqs->cnt, j));

	}

	if (desc->kstat_irqs)

		any_count = kstat_irqs_desc(desc, cpu_online_mask);



	if ((!desc->action || irq_desc_is_chained(desc)) && !any_count)

		goto outsparse;