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

Bitao Hu
2024-02-26T02:10:00Z

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)
--
2.37.1 (Apple Git-137.1)