From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AC326C433F5 for ; Tue, 16 Nov 2021 02:11:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9705C61AAA for ; Tue, 16 Nov 2021 02:11:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345864AbhKPCOX (ORCPT ); Mon, 15 Nov 2021 21:14:23 -0500 Received: from mail.kernel.org ([198.145.29.99]:40768 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239146AbhKORyo (ORCPT ); Mon, 15 Nov 2021 12:54:44 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id A4225632BE; Mon, 15 Nov 2021 17:33:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1636997593; bh=K7nlG8HgYzu9WQ9jWs0uyzdRTJRrzl3CIfHvUM1TOyo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=gEacw0D9PFMpIDR45YAlHfjfL/oKnvTF3vczykS3UfwK3oeAe5xUs+xQpBBLS/TaE 8kxibefLg/7njzwrlpOGpF1aWhLQz0Uxw3RsZRrm+zc883tOnsYocapFcQ9vkG6fl+ KaaJzVxox6cyMViG6203Mlg4CAwLSJbd4kya6ioc= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Luigi Rizzo , Josh Don , "Peter Zijlstra (Intel)" , Eric Dumazet , Sasha Levin Subject: [PATCH 5.10 204/575] fs/proc/uptime.c: Fix idle time reporting in /proc/uptime Date: Mon, 15 Nov 2021 17:58:49 +0100 Message-Id: <20211115165350.768569909@linuxfoundation.org> X-Mailer: git-send-email 2.33.1 In-Reply-To: <20211115165343.579890274@linuxfoundation.org> References: <20211115165343.579890274@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Josh Don [ Upstream commit a130e8fbc7de796eb6e680724d87f4737a26d0ac ] /proc/uptime reports idle time by reading the CPUTIME_IDLE field from the per-cpu kcpustats. However, on NO_HZ systems, idle time is not continually updated on idle cpus, leading this value to appear incorrectly small. /proc/stat performs an accounting update when reading idle time; we can use the same approach for uptime. With this patch, /proc/stat and /proc/uptime now agree on idle time. Additionally, the following shows idle time tick up consistently on an idle machine: (while true; do cat /proc/uptime; sleep 1; done) | awk '{print $2-prev; prev=$2}' Reported-by: Luigi Rizzo Signed-off-by: Josh Don Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Eric Dumazet Link: https://lkml.kernel.org/r/20210827165438.3280779-1-joshdon@google.com Signed-off-by: Sasha Levin --- fs/proc/stat.c | 4 ++-- fs/proc/uptime.c | 14 +++++++++----- include/linux/kernel_stat.h | 1 + 3 files changed, 12 insertions(+), 7 deletions(-) diff --git a/fs/proc/stat.c b/fs/proc/stat.c index 4695b6de31512..3bed48d8228b4 100644 --- a/fs/proc/stat.c +++ b/fs/proc/stat.c @@ -23,7 +23,7 @@ #ifdef arch_idle_time -static u64 get_idle_time(struct kernel_cpustat *kcs, int cpu) +u64 get_idle_time(struct kernel_cpustat *kcs, int cpu) { u64 idle; @@ -45,7 +45,7 @@ static u64 get_iowait_time(struct kernel_cpustat *kcs, int cpu) #else -static u64 get_idle_time(struct kernel_cpustat *kcs, int cpu) +u64 get_idle_time(struct kernel_cpustat *kcs, int cpu) { u64 idle, idle_usecs = -1ULL; diff --git a/fs/proc/uptime.c b/fs/proc/uptime.c index 5a1b228964fb7..deb99bc9b7e6b 100644 --- a/fs/proc/uptime.c +++ b/fs/proc/uptime.c @@ -12,18 +12,22 @@ static int uptime_proc_show(struct seq_file *m, void *v) { struct timespec64 uptime; struct timespec64 idle; - u64 nsec; + u64 idle_nsec; u32 rem; int i; - nsec = 0; - for_each_possible_cpu(i) - nsec += (__force u64) kcpustat_cpu(i).cpustat[CPUTIME_IDLE]; + idle_nsec = 0; + for_each_possible_cpu(i) { + struct kernel_cpustat kcs; + + kcpustat_cpu_fetch(&kcs, i); + idle_nsec += get_idle_time(&kcs, i); + } ktime_get_boottime_ts64(&uptime); timens_add_boottime(&uptime); - idle.tv_sec = div_u64_rem(nsec, NSEC_PER_SEC, &rem); + idle.tv_sec = div_u64_rem(idle_nsec, NSEC_PER_SEC, &rem); idle.tv_nsec = rem; seq_printf(m, "%lu.%02lu %lu.%02lu\n", (unsigned long) uptime.tv_sec, diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h index 89f0745c096d4..8fff3500d50ee 100644 --- a/include/linux/kernel_stat.h +++ b/include/linux/kernel_stat.h @@ -103,6 +103,7 @@ extern void account_system_index_time(struct task_struct *, u64, enum cpu_usage_stat); extern void account_steal_time(u64); extern void account_idle_time(u64); +extern u64 get_idle_time(struct kernel_cpustat *kcs, int cpu); #ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE static inline void account_process_tick(struct task_struct *tsk, int user) -- 2.33.0