From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 3AADC37CD33 for ; Tue, 29 Sep 2026 13:50:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790689836; cv=none; b=PJPs0X6v2UvNv0b8Ef2IxNWPjJD9aTzL4fJO++Xidt9Z77ZNRPrDMZW/kEZh4CHScN8/U7BseWvMoGnHm/5cNwgRBix++TbhkwLEQk9S+/C5IgpzHY9cPEILnMQfcgph4eU7wXeDG2tN/+x7NmfsYP9Ahln9EWfWs3KIvIrTSnQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790689836; c=relaxed/simple; bh=pkAjWq2qsb19Kk+6tfhOQNlRNmYwaVCv5Tvkoq23pbI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=fPljJXHzT+Ia3DjhdDegy5LTpKM+9L9doCgPvJYA0v/8tuU73A9g+Gr7uoD+z0GVJvjNnn0JnpifRGswvxcXt5E9EPkPe7OSM5r7McPkvXxM2WbaKySito2MPjHg3EJ/vGu8iIGc+QXedBqD6qKSqw2RjT2xrnYpEQmHiGMWGeQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=SyacP3nW; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="SyacP3nW" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 53AC21F000FF; Tue, 29 Sep 2026 13:50:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790689834; bh=d138TUO/Ve/2vyNV5jB3KW2+RQ5rrXezbHRlOxWZDsQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=SyacP3nWMNBV1SC6yyhzxJ+HX5GPxeyKX0jmfrqPjjF0bkiowzwoPsABDbSAwzJZV XQgmhmMjUPrRhBFmHuWC0mQ725Qg72Da1bZ4aB+39lB+Uq9nxgvVJCZIC6sU2hW3wo Ode8YQaH74wF9w1RTS4yI/ZMxe5SXenH5d9IG7yI+brD82yZQQtXy5PxUrZwuOdt5s B6nKHxsQvZZJJVK6QSuHFAbntn+9e0nqZykWOvYeu0m8npDJ/j/kvg+k6tftE1kSdr Vpls2MRHNiHjmg5Zn532+cnVOYTu966sZzDE5f9MX6pOoxfBxqCbW4unRSajZo0urG WYr22xJw6Azhg== Date: Tue, 29 Sep 2026 15:50:31 +0200 From: Frederic Weisbecker To: Ahmed Shaltout Cc: tglx@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [REGRESSION] /proc/stat idle time exceeds wall clock since v7.2 Message-ID: References: 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=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Le Tue, Sep 22, 2026 at 07:53:23PM +0400, Ahmed Shaltout a écrit : > Hi Frederic, > > Le Mon, Sep 21, 2026, Frederic Weisbecker a écrit : > > I can't manage to reproduce that, neither on latest mainline nor on 7.2.7 > > > > Can you share your whole .config file? > > Attached: config-7.2.5-1-default, taken from /boot/config-$(uname -r) on an > affected node. It is the stock openSUSE Tumbleweed/MicroOS package > kernel-default-7.2.5-1.1.x86_64, unmodified, no custom build. It differs > from > config/x86_64/default in openSUSE:Factory/kernel-source at the 7.2.5 source > revision only in toolchain-detection and build-metadata lines (CC/AS/LD > version, LOCALVERSION, MODULE_SIG_KEY, CC_HAS_*), no functional option: > https://api.opensuse.org/public/source/openSUSE:Factory/kernel-source/config.tar.bz2?rev=4dabae0b715184e35b05b9a168bde6b7 I fear I still can't reproduce with the config in attachment. > > The unaffected control box runs kernel-default-7.1.8-1.1.x86_64 from the > same > distribution, also stock, same VM type, same command line. Between the two > configs the only change among the scheduler, tick, accounting, preemption > and > RCU options is CONFIG_SCHED_CACHE=y appearing in 7.2.5. > > Environment, in case it is what your test box does not share: > > - Every node is a KVM guest (Hetzner Cloud, QEMU, "AMD EPYC-Rome > Processor", > 8 vCPUs, one with 4), clocksource kvm-clock. > - No steal-time accounting at all: there is no kvm-stealtime line in the > boot log and the steal column has read exactly 0 on every node for the > 75 hours since boot, so the hypervisor does not seem to expose the MSR. > - CONFIG_VIRT_CPU_ACCOUNTING_GEN=y, CONFIG_CONTEXT_TRACKING_IDLE=y and > CONFIG_NO_HZ_FULL=y are built in (SUSE default) with nohz_full= empty, > so the CPUs run idle dynticks, not full. > - CONFIG_HZ=1000, CONFIG_PREEMPT_DYNAMIC=y, psi=1 on the command line: > BOOT_IMAGE=/boot/vmlinuz-7.2.5-1-default root=UUID=... rd.timeout=60 > rd.retry=45 quiet systemd.show_status=yes console=ttyS0,115200 > console=tty0 ignition.platform.id=openstack security=selinux selinux=1 > psi=1 I ran on KVM too, overcommiting the vcpus like you did (16 vCPUs on 8 CPUs) and still nothing wrong. I'm wondering if this is specific to opensuse somehow. Can you try to build the latest upstream kernel? Thanks. -- Frederic Weisbecker SUSE Labs