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 BEE783BAD90 for ; Fri, 20 Mar 2026 13:22:18 +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=1774012938; cv=none; b=jFx/e3B/hlQdnderTBXQOpXCFYtdOSIB863pDNyCiLCJ/f9NjUKHW3V4dnIkBb7So756zA/54FPXAtt/nBsbJhoyHZ2QYZKI/2AlPzwv8GyHu9bDlZl8qsbOq1Z1rMYgztb/NmGk+QRfe9i0PMqk/dCxG2aMRYvv0Jgoj7a+LmE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774012938; c=relaxed/simple; bh=O3APnRX8qmvXPCKagjJK3cyA8Md07uXBTpZEDOrJFKA=; h=Date:Message-ID:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=OwT6b6/p0h2IyWMJWeC2gNY2Ka2gqQkwM8Qz401gKkzT6eiP3XGqdIAYWFV6/5ybGTF282NCivWarXceOLyGr0oA8d5yhK3m8EdEUO1PRiE8AiGhYHKL7D3JqOiG+13KwA3R3SnGE109g6ytdmLXXC2ZmXOpV9FzRDiKu3SIxrI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=rvOksWJE; 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="rvOksWJE" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A8EF5C4CEF7; Fri, 20 Mar 2026 13:22:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774012938; bh=O3APnRX8qmvXPCKagjJK3cyA8Md07uXBTpZEDOrJFKA=; h=Date:From:To:Cc:Subject:References:From; b=rvOksWJET9wMmA6fmXzwYMtrYHoKJnI4SicjAo0HPYAdsIUMdUJXG/U41EMmYKV6N roG0fxWkulwp/YMBoRXQUuWKy5hUqAhEp19HS4/MGp2jY/oKAUol3Ia9v8VUuxh2oY otZd0V9kQO3wooY0EKhnnqQMUOm/hTFn3dYAKEqd8mANYknKMjLRmFyXHfdpMS4Gy7 qk3LcTaXqY2Ue8fKM7mt5wWnTfZ886ytR4SIfNlYatCa0zvdjiN1MnawpdjE5TJLDM RVAYTckW5jJj8g/FtXbPo2Kz26ifN+2I8YHvD+7L4L+wkHkP1AZuE4qOoVCajyUFLn 0floGzNfqbv6A== Date: Fri, 20 Mar 2026 14:22:14 +0100 Message-ID: <20260320132102.706440131@kernel.org> User-Agent: quilt/0.68 From: Thomas Gleixner To: LKML Cc: x86@kernel.org, Dmitry Ilvokhin , Neil Horman , Radu Rendec Subject: [patch v2 10/14] genirq/proc: Speed up /proc/interrupts iteration References: <20260320131108.344376329@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 | 99 +++++++++++++++++++++++++++++++++++++++++++----------- 2 files changed, 83 insertions(+), 20 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 @@ -452,6 +452,8 @@ 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; @@ -508,34 +510,29 @@ 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) { - int prec = READ_ONCE(irq_num_prec); - - int i = *(loff_t *) v, j; + int prec = (int)(unsigned long)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) + if (desc == ARCH_PROC_IRQDESC) return arch_show_interrupts(p, prec); - /* print header and calculate the width of the first column */ - if (i == 0) { + /* print header for the first interrupt indicated by !p>private */ + if (!prec) { + unsigned int cpu; + + prec = READ_ONCE(irq_num_prec); seq_printf(p, "%*s", prec + 8, ""); - for_each_online_cpu(j) - seq_printf(p, "CPU%-8d", j); + for_each_online_cpu(cpu) + seq_printf(p, "CPU%-8d", cpu); seq_putc(p, '\n'); + p->private = (void *)(unsigned long)prec; } - 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), prec); + seq_putc(p, ':'); /* * Always output per CPU interrupts. Output device interrupts only when @@ -582,4 +579,68 @@ int show_interrupts(struct seq_file *p, seq_putc(p, '\n'); return 0; } + +static void *irq_seq_next_desc(loff_t *pos) +{ + struct irq_desc *desc; + + if (*pos > total_nr_irqs) + return NULL; + + guard(rcu)(); + for (;;) { + 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) + f->private = NULL; + 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("interrupts", 0, NULL, &irq_seq_ops); + return 0; +} +fs_initcall(irq_proc_init); + #endif