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genirq/proc: Avoid formatting zero counts in /proc/interrupts

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A large portion of interrupt count entries are zero. There is no point in
formatting the zero value as it is way cheeper to just emit a constant
string.

Collect the number of consecutive zero counts and emit them in one go
before a non-zero count and at the end of the line.

Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Michael Kelley <mhklinux@outlook.com>
Reviewed-by: Dmitry Ilvokhin <d@ilvokhin.com>
Reviewed-by: Radu Rendec <radu@rendec.net>
Reviewed-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Link: https://patch.msgid.link/20260517194931.034728540@kernel.org
This commit is contained in:
Thomas Gleixner
2026-05-17 22:01:38 +02:00
parent 115bbf0c1b
commit 95c33a64f2
2 changed files with 39 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/interrupt.h
View File

@@ -864,6 +864,7 @@ static inline void init_irq_proc(void)
struct seq_file;
int show_interrupts(struct seq_file *p, void *v);
int arch_show_interrupts(struct seq_file *p, int prec);
void irq_proc_emit_counts(struct seq_file *p, unsigned int __percpu *cnts);
extern int early_irq_init(void);
extern int arch_probe_nr_irqs(void);

43
kernel/irq/proc.c
View File

@@ -451,6 +451,43 @@ int __weak arch_show_interrupts(struct seq_file *p, int prec)
# define ACTUAL_NR_IRQS irq_get_nr_irqs()
#endif
/* Same as seq_put_decimal_ull_width(p, " ", cnt, 10) */
#define ZSTR1 " 0"
#define ZSTR1_LEN (sizeof(ZSTR1) - 1)
#define ZSTR16 ZSTR1 ZSTR1 ZSTR1 ZSTR1 ZSTR1 ZSTR1 ZSTR1 ZSTR1 \
ZSTR1 ZSTR1 ZSTR1 ZSTR1 ZSTR1 ZSTR1 ZSTR1 ZSTR1
#define ZSTR256 ZSTR16 ZSTR16 ZSTR16 ZSTR16 ZSTR16 ZSTR16 ZSTR16 ZSTR16 \
ZSTR16 ZSTR16 ZSTR16 ZSTR16 ZSTR16 ZSTR16 ZSTR16 ZSTR16
static inline void irq_proc_emit_zero_counts(struct seq_file *p, unsigned int zeros)
{
if (!zeros)
return;
for (unsigned int n = min(zeros, 256); n; zeros -= n, n = min(zeros, 256))
seq_write(p, ZSTR256, n * ZSTR1_LEN);
}
static inline unsigned int irq_proc_emit_count(struct seq_file *p, unsigned int cnt,
unsigned int zeros)
{
if (!cnt)
return zeros + 1;
irq_proc_emit_zero_counts(p, zeros);
seq_put_decimal_ull_width(p, " ", cnt, 10);
return 0;
}
void irq_proc_emit_counts(struct seq_file *p, unsigned int __percpu *cnts)
{
unsigned int cpu, zeros = 0;
for_each_online_cpu(cpu)
zeros = irq_proc_emit_count(p, per_cpu(*cnts, cpu), zeros);
irq_proc_emit_zero_counts(p, zeros);
}
int show_interrupts(struct seq_file *p, void *v)
{
const unsigned int nr_irqs = irq_get_nr_irqs();
@@ -486,11 +523,7 @@ int show_interrupts(struct seq_file *p, void *v)
return 0;
seq_printf(p, "%*d:", prec, i);
for_each_online_cpu(j) {
unsigned int cnt = desc->kstat_irqs ? per_cpu(desc->kstat_irqs->cnt, j) : 0;
seq_put_decimal_ull_width(p, " ", cnt, 10);
}
irq_proc_emit_counts(p, &desc->kstat_irqs->cnt);
seq_putc(p, ' ');
guard(raw_spinlock_irq)(&desc->lock);