From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C430531A072 for ; Thu, 26 Mar 2026 21:58:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774562292; cv=none; b=HsbrfTwJi1OTiCBtSbb9/nvh/7HLYEDQMecQW5DFzGzPgUhKP1aKTsp8IEkRdBzC+YkgQQzNamK+sCBQc2Xt9pLiwBR3+RPsbmb2/KNxIbMowG4kh310+hc9HL7e24KCUZKJ/JWSiORGpk6kjg8DANBJtKFaL+5kdFBqxbmD1RY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774562292; c=relaxed/simple; bh=G1dw7uFOW9FaQ1UfF2dFkBOfrQ2cCB0+LUEx1oWKcxs=; h=Date:Message-ID:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=Ud7ydxKRqSeZp/btFR5sAmIRzmFF+SciJohojf7MphDEY3+jER4Emy1Ria79MZK/Qg7waTq3iBylySPVHHPf23r+b300/Dbmnq+Nsg2sJ1Js5x3I1UB/z4ivonj6YslRxbqc3dltzvhCdbSWAlS7cvwCZjYCtsJxYE0weltFXrU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=VuItKb2R; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="VuItKb2R" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D8BE5C116C6; Thu, 26 Mar 2026 21:58:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774562292; bh=G1dw7uFOW9FaQ1UfF2dFkBOfrQ2cCB0+LUEx1oWKcxs=; h=Date:From:To:Cc:Subject:References:From; b=VuItKb2Ra+WvkeDZqOGE02tJQLJ4CP0RAMIXyfNgVIMGBPhdlGfuSQd0wji3bi4bq 35FLHf37HYEoopV9JI8jLdlImC/m0SOBYHxDabrafJSNpqMOb0PPouRxW4Aa1J95DE pTpm0+7QwhpvdDix+GdbavrnUl2kZ0qt8bOOaEPA4ZodPckc+W/UZADxAfqMJPfFJO bmBy4kBYKOAUPLBcJiCnbbHDqYBswKkav/Nanr0E/IMSV7BSQNvkZnNRH2ZnlE2z8c rHIQK5lbXYgc0U4OsSQhkZAkKeEZPKwPsJiN4Q1vmcEVpBchxzkG+04uLEtg8THtFs RhtCoEXXBKcQA== Date: Thu, 26 Mar 2026 22:58:07 +0100 Message-ID: <20260326215037.186093902@kernel.org> User-Agent: quilt/0.68 From: Thomas Gleixner To: LKML Cc: x86@kernel.org, Michael Kelley , Dmitry Ilvokhin , Radu Rendec , Jan Kiszka , Kieran Bingham , Florian Fainelli Subject: [patch V3 14/14] genirq/proc: Speed up /proc/interrupts iteration References: <20260326214345.019130211@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 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 --- fs/proc/Makefile | 4 + kernel/irq/proc.c | 118 ++++++++++++++++++++++++++++++++++++++++++------------ 2 files changed, 95 insertions(+), 27 deletions(-) --- 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 --- a/kernel/irq/proc.c +++ b/kernel/irq/proc.c @@ -451,6 +451,8 @@ void irq_proc_update_valid(struct irq_de #ifdef CONFIG_GENERIC_IRQ_SHOW +#define ARCH_PROC_IRQDESC ((void *)0x00001111) + int __weak arch_show_interrupts(struct seq_file *p, int prec) { return 0; @@ -459,6 +461,7 @@ int __weak arch_show_interrupts(struct s 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 = { @@ -531,34 +534,28 @@ void irq_proc_emit_counts(struct seq_fil 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; - if (i == ACTUAL_NR_IRQS) - return arch_show_interrupts(p, prec); + if (desc == ARCH_PROC_IRQDESC) + return arch_show_interrupts(p, constr->num_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); + /* print header for the first interrupt indicated by !p>private */ + if (constr->print_header) { + unsigned int cpu; + + 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; - - 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 @@ -578,18 +575,18 @@ int show_interrupts(struct seq_file *p, 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"); @@ -607,4 +604,73 @@ int show_interrupts(struct seq_file *p, 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 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