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genirq: Speedup show_interrupts()

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Since commit 425a5072dc ("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 <edumazet@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Link: https://lkml.kernel.org/r/20180620150332.163320-1-edumazet@google.com
This commit is contained in:
Eric Dumazet 2018-06-20 08:03:32 -07:00 committed by Thomas Gleixner
parent 0a13ec0bbc
commit 74bdf7815d
1 changed files with 12 additions and 10 deletions
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22
kernel/irq/proc.c
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@ -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