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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2B423C43217 for ; Wed, 23 Nov 2022 00:26:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235248AbiKWA0g (ORCPT ); Tue, 22 Nov 2022 19:26:36 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48422 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233044AbiKWA0e (ORCPT ); Tue, 22 Nov 2022 19:26:34 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B06E7BEAFE; Tue, 22 Nov 2022 16:26:33 -0800 (PST) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 4C66D6195A; Wed, 23 Nov 2022 00:26:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id AA4D4C433D7; Wed, 23 Nov 2022 00:26:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1669163192; bh=5i9nIHhwqVmvzh0mZrit4SoCEiwLPbgmrDJj5rqrRgU=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=tBHUL+xpCr7xsHdi93mvRd57hGmh17xvE1BxlCxFo285BigX+OE7Xktsrqn6oBYLH kqIvKjs7mBQvth52bMPO/FkDcnYi2buNCjQBDntCW6eUzACs0rhpMLd/dGjQRWbZyk c+NsAjy8a+wkoToXIN4dTbaWCqPyROsGn2zIP/0kH5dvLiT3f5jK5/KAl4npVfQLS+ c5FC80NYnuDa40azbBXoYCwIjLaUrN5Gin0Am2rvPy6MXCxcveszwtIixN6HM00kD0 AxOagvzKMn8GiXE/ZqcMf8QVzabOzpzqTaERXSSbpncyswWbjXZq3aqgPRlRd0fBIm iBeo7BP3zGtrA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 4B0405C0BE7; Tue, 22 Nov 2022 16:26:32 -0800 (PST) Date: Tue, 22 Nov 2022 16:26:32 -0800 From: "Paul E. McKenney" To: "Leizhen (ThunderTown)" Cc: Frederic Weisbecker , Neeraj Upadhyay , Josh Triplett , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , rcu@vger.kernel.org, linux-kernel@vger.kernel.org, Robert Elliott Subject: Re: [PATCH v8 0/6] rcu: Add RCU stall diagnosis information Message-ID: <20221123002632.GS4001@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <20221119092508.1766-1-thunder.leizhen@huawei.com> <20221121222910.GP4001@paulmck-ThinkPad-P17-Gen-1> <6877d891-7314-d9b3-5e1a-3e6bd239489b@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6877d891-7314-d9b3-5e1a-3e6bd239489b@huawei.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 22, 2022 at 10:14:04AM +0800, Leizhen (ThunderTown) wrote: > > > On 2022/11/22 6:29, Paul E. McKenney wrote: > > On Sat, Nov 19, 2022 at 05:25:02PM +0800, Zhen Lei wrote: > >> v7 --> v8: > >> 1. Change call jiffies64_to_msecs() to call jiffies_to_msecs(). > >> 2. Mention that rcupdate.rcu_cpu_stall_cputime overrides > >> CONFIG_RCU_CPU_STALL_CPUTIME behaviour in the Kconfig help text. > >> 3. Fix a make htmldocs warning, change "|...|" to ":...:". > >> > >> v6 --> v7: > >> 1. Use kcpustat_field() to obtain the cputime. > >> 2. Make the output start with "\t" to match other related prints. > >> 3. Aligns the output of the last line of RCU stall. > >> > >> v5 --> v6: > >> 1. When there are more than two continuous RCU stallings, correctly handle the > >> value of the second and subsequent sampling periods. Update comments and > >> document. > >> Thanks to Elliott, Robert for the test. > >> 2. Change "rcu stall" to "RCU stall". > >> > >> v4 --> v5: > >> 1. Resolve a git am conflict. No code change. > >> > >> v3 --> v4: > >> 1. Rename rcu_cpu_stall_deep_debug to rcu_cpu_stall_cputime. > >> > >> v2 --> v3: > >> 1. Fix the return type of kstat_cpu_irqs_sum() > >> 2. Add Kconfig option CONFIG_RCU_CPU_STALL_DEEP_DEBUG and boot parameter > >> rcupdate.rcu_cpu_stall_deep_debug. > >> 3. Add comments and normalize local variable name > >> > >> v1 --> v2: > >> 1. Fixed a bug in the code. If the rcu stall is detected by another CPU, > >> kcpustat_this_cpu cannot be used. > >> @@ -451,7 +451,7 @@ static void print_cpu_stat_info(int cpu) > >> if (r->gp_seq != rdp->gp_seq) > >> return; > >> > >> - cpustat = kcpustat_this_cpu->cpustat; > >> + cpustat = kcpustat_cpu(cpu).cpustat; > >> 2. Move the start point of statistics from rcu_stall_kick_kthreads() to > >> rcu_implicit_dynticks_qs(), removing the dependency on irq_work. > >> > >> v1: > >> In some extreme cases, such as the I/O pressure test, the CPU usage may > >> be 100%, causing RCU stall. In this case, the printed information about > >> current is not useful. Displays the number and usage of hard interrupts, > >> soft interrupts, and context switches that are generated within half of > >> the CPU stall timeout, can help us make a general judgment. In other > >> cases, we can preliminarily determine whether an infinite loop occurs > >> when local_irq, local_bh or preempt is disabled. > > > > Queued for further review and testing, thank you! > > > > I did the usual wordsmithing, so please check to see if I messed > > something up. > > Thanks for your help. > > Sorry, I think I missed a word in the commit message of patch 5/6. > > This commit documents the additional RCU CPU stall warning output produced > - by kernels built with CONFIG_RCU_CPU_STALL_CPUTIME=y. > + by kernels built with CONFIG_RCU_CPU_STALL_CPUTIME=y or booted with > + rcupdate.rcu_cpu_stall_cputime=1. Good eyes, fixed, thank you! Thanx, Paul > >> Zhen Lei (6): > >> genirq: Fix the return type of kstat_cpu_irqs_sum() > >> sched: Add helper kstat_cpu_softirqs_sum() > >> sched: Add helper nr_context_switches_cpu() > >> rcu: Add RCU stall diagnosis information > >> doc: Document CONFIG_RCU_CPU_STALL_CPUTIME=y stall information > >> rcu: Align the output of RCU stall > >> > >> Documentation/RCU/stallwarn.rst | 88 +++++++++++++++++++ > >> .../admin-guide/kernel-parameters.txt | 6 ++ > >> include/linux/kernel_stat.h | 14 ++- > >> kernel/rcu/Kconfig.debug | 13 +++ > >> kernel/rcu/rcu.h | 1 + > >> kernel/rcu/tree.c | 18 ++++ > >> kernel/rcu/tree.h | 19 ++++ > >> kernel/rcu/tree_stall.h | 35 +++++++- > >> kernel/rcu/update.c | 2 + > >> kernel/sched/core.c | 5 ++ > >> 10 files changed, 198 insertions(+), 3 deletions(-) > >> > >> -- > >> 2.25.1 > >> > > . > > > > -- > Regards, > Zhen Lei