From: Thomas Gleixner Date: Sun, 17 May 2026 20:02:49 +0000 (+0200) Subject: genirq/proc: Speed up /proc/interrupts iteration X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=171cc0d9eed1cad5de7ce6a212efbeda390edb0f;p=thirdparty%2Fkernel%2Flinux.git genirq/proc: Speed up /proc/interrupts iteration Reading /proc/interrupts iterates over the interrupt number space one by one and looks up the descriptors one by one. That's just a waste of time. When CONFIG_GENERIC_IRQ_SHOW is enabled this can utilize the maple tree and cache the descriptor pointer efficiently for the sequence file operations. Implement a CONFIG_GENERIC_IRQ_SHOW specific version in the core code and leave the fs/proc/ variant for the legacy architectures which ignore generic code. This reduces the time wasted for looking up the next record significantly. Signed-off-by: Thomas Gleixner Tested-by: Michael Kelley Reviewed-by: Dmitry Ilvokhin Link: https://patch.msgid.link/20260517194932.165280601@kernel.org --- diff --git a/fs/proc/Makefile b/fs/proc/Makefile index 7b4db9c56e6a7..8bc615ff84e5d 100644 --- a/fs/proc/Makefile +++ b/fs/proc/Makefile @@ -16,7 +16,9 @@ proc-y += cmdline.o proc-y += consoles.o proc-y += cpuinfo.o proc-y += devices.o -proc-y += interrupts.o +ifneq ($(CONFIG_GENERIC_IRQ_SHOW),y) +proc-y += interrupts.o +endif proc-y += loadavg.o proc-y += meminfo.o proc-y += stat.o diff --git a/kernel/irq/proc.c b/kernel/irq/proc.c index 9a968007eb2d1..1b835725f7b1c 100644 --- a/kernel/irq/proc.c +++ b/kernel/irq/proc.c @@ -452,6 +452,8 @@ void irq_proc_update_valid(struct irq_desc *desc) #ifdef CONFIG_GENERIC_IRQ_SHOW +#define ARCH_PROC_IRQDESC ((void *)0x00001111) + int __weak arch_show_interrupts(struct seq_file *p, int prec) { return 0; @@ -460,6 +462,7 @@ int __weak arch_show_interrupts(struct seq_file *p, int prec) static DEFINE_RAW_SPINLOCK(irq_proc_constraints_lock); static struct irq_proc_constraints { + bool print_header; unsigned int num_prec; unsigned int chip_width; } irq_proc_constraints __read_mostly = { @@ -533,34 +536,28 @@ void irq_proc_emit_counts(struct seq_file *p, unsigned int __percpu *cnts) irq_proc_emit_zero_counts(p, zeros); } -int show_interrupts(struct seq_file *p, void *v) +static int irq_seq_show(struct seq_file *p, void *v) { - unsigned int chip_width = READ_ONCE(irq_proc_constraints.chip_width); - unsigned int prec = READ_ONCE(irq_proc_constraints.num_prec); - int i = *(loff_t *) v, j; + struct irq_proc_constraints *constr = p->private; + struct irq_desc *desc = v; struct irqaction *action; - struct irq_desc *desc; - if (i > ACTUAL_NR_IRQS) - return 0; + /* Print header for the first interrupt? */ + if (constr->print_header) { + unsigned int cpu; - if (i == ACTUAL_NR_IRQS) - return arch_show_interrupts(p, prec); - - /* print header and calculate the width of the first column */ - if (i == 0) { - seq_printf(p, "%*s", prec + 8, ""); - for_each_online_cpu(j) - seq_printf(p, "CPU%-8d", j); + seq_printf(p, "%*s", constr->num_prec + 8, ""); + for_each_online_cpu(cpu) + seq_printf(p, "CPU%-8d", cpu); seq_putc(p, '\n'); + constr->print_header = false; } - guard(rcu)(); - desc = irq_to_desc(i); - if (!desc || !irq_settings_proc_valid(desc)) - return 0; + if (desc == ARCH_PROC_IRQDESC) + return arch_show_interrupts(p, constr->num_prec); - seq_printf(p, "%*d:", prec, i); + seq_put_decimal_ull_width(p, "", irq_desc_get_irq(desc), constr->num_prec); + seq_putc(p, ':'); /* * Always output per CPU interrupts. Output device interrupts only when @@ -580,18 +577,18 @@ int show_interrupts(struct seq_file *p, void *v) if (desc->irq_data.chip->irq_print_chip) desc->irq_data.chip->irq_print_chip(&desc->irq_data, p); else if (desc->irq_data.chip->name) - seq_printf(p, "%-*s", chip_width, desc->irq_data.chip->name); + seq_printf(p, "%-*s", constr->chip_width, desc->irq_data.chip->name); else - seq_printf(p, "%-*s", chip_width, "-"); + seq_printf(p, "%-*s", constr->chip_width, "-"); } else { - seq_printf(p, "%-*s", chip_width, "None"); + seq_printf(p, "%-*s", constr->chip_width, "None"); } seq_putc(p, ' '); if (desc->irq_data.domain) - seq_put_decimal_ull_width(p, "", desc->irq_data.hwirq, prec); + seq_put_decimal_ull_width(p, "", desc->irq_data.hwirq, constr->num_prec); else - seq_printf(p, " %*s", prec, ""); + seq_printf(p, " %*s", constr->num_prec, ""); if (IS_ENABLED(CONFIG_GENERIC_IRQ_SHOW_LEVEL)) seq_printf(p, " %-8s", irqd_is_level_type(&desc->irq_data) ? "Level" : "Edge"); @@ -609,4 +606,73 @@ int show_interrupts(struct seq_file *p, void *v) seq_putc(p, '\n'); return 0; } + +static void *irq_seq_next_desc(loff_t *pos) +{ + if (*pos > total_nr_irqs) + return NULL; + + guard(rcu)(); + for (;;) { + struct irq_desc *desc = irq_find_desc_at_or_after((unsigned int) *pos); + + if (desc) { + *pos = irq_desc_get_irq(desc); + /* + * If valid for output then try to acquire a reference + * count on the descriptor so that it can't be freed + * after dropping RCU read lock on return. + */ + if (irq_settings_proc_valid(desc) && irq_desc_get_ref(desc)) + return desc; + (*pos)++; + } else { + *pos = total_nr_irqs; + return ARCH_PROC_IRQDESC; + } + } +} + +static void *irq_seq_start(struct seq_file *f, loff_t *pos) +{ + if (!*pos) { + struct irq_proc_constraints *constr = f->private; + + constr->num_prec = READ_ONCE(irq_proc_constraints.num_prec); + constr->chip_width = READ_ONCE(irq_proc_constraints.chip_width); + constr->print_header = true; + } + return irq_seq_next_desc(pos); +} + +static void *irq_seq_next(struct seq_file *f, void *v, loff_t *pos) +{ + if (v && v != ARCH_PROC_IRQDESC) + irq_desc_put_ref(v); + + (*pos)++; + return irq_seq_next_desc(pos); +} + +static void irq_seq_stop(struct seq_file *f, void *v) +{ + if (v && v != ARCH_PROC_IRQDESC) + irq_desc_put_ref(v); +} + +static const struct seq_operations irq_seq_ops = { + .start = irq_seq_start, + .next = irq_seq_next, + .stop = irq_seq_stop, + .show = irq_seq_show, +}; + +static int __init irq_proc_init(void) +{ + proc_create_seq_private("interrupts", 0, NULL, &irq_seq_ops, + sizeof(irq_proc_constraints), NULL); + return 0; +} +fs_initcall(irq_proc_init); + #endif