From 74bdf7815dfb3805a37b0bba615814063a227bf5 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 20 Jun 2018 08:03:32 -0700 Subject: [PATCH] genirq: Speedup show_interrupts() Since commit 425a5072dcd1 ("genirq: Free irq_desc with rcu"), show_interrupts() can be switched to rcu locking, which removes possible contention on sparse_irq_lock. The per_cpu count scan and print can be done without holding desc spinlock. And there is no need to call kstat_irqs_cpu() and abuse irq_to_desc() while holding rcu read lock, since desc and desc->kstat_irqs wont disappear or change. Signed-off-by: Eric Dumazet Signed-off-by: Thomas Gleixner Cc: Eric Dumazet Link: https://lkml.kernel.org/r/20180620150332.163320-1-edumazet@google.com --- kernel/irq/proc.c | 22 ++++++++++++---------- 1 file changed, 12 insertions(+), 10 deletions(-) diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c index 37eda10f5c36..da9addb8d655 100644 --- a/kernel/irq/proc.c +++ b/kernel/irq/proc.c @@ -475,22 +475,24 @@ int show_interrupts(struct seq_file *p, void *v) seq_putc(p, '\n'); } - irq_lock_sparse(); + rcu_read_lock(); desc = irq_to_desc(i); if (!desc) goto outsparse; - raw_spin_lock_irqsave(&desc->lock, flags); - for_each_online_cpu(j) - any_count |= kstat_irqs_cpu(i, j); - action = desc->action; - if ((!action || irq_desc_is_chained(desc)) && !any_count) - goto out; + if (desc->kstat_irqs) + for_each_online_cpu(j) + any_count |= *per_cpu_ptr(desc->kstat_irqs, j); + + if ((!desc->action || irq_desc_is_chained(desc)) && !any_count) + goto outsparse; seq_printf(p, "%*d: ", prec, i); for_each_online_cpu(j) - seq_printf(p, "%10u ", kstat_irqs_cpu(i, j)); + seq_printf(p, "%10u ", desc->kstat_irqs ? + *per_cpu_ptr(desc->kstat_irqs, j) : 0); + raw_spin_lock_irqsave(&desc->lock, flags); if (desc->irq_data.chip) { if (desc->irq_data.chip->irq_print_chip) desc->irq_data.chip->irq_print_chip(&desc->irq_data, p); @@ -511,6 +513,7 @@ int show_interrupts(struct seq_file *p, void *v) if (desc->name) seq_printf(p, "-%-8s", desc->name); + action = desc->action; if (action) { seq_printf(p, " %s", action->name); while ((action = action->next) != NULL) @@ -518,10 +521,9 @@ int show_interrupts(struct seq_file *p, void *v) } seq_putc(p, '\n'); -out: raw_spin_unlock_irqrestore(&desc->lock, flags); outsparse: - irq_unlock_sparse(); + rcu_read_unlock(); return 0; } #endif -- 2.30.2