From patchwork Mon Oct 17 10:01:06 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Leizhen (ThunderTown)" X-Patchwork-Id: 13008487 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 77034C43217 for ; Mon, 17 Oct 2022 10:02:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230420AbiJQKB7 (ORCPT ); Mon, 17 Oct 2022 06:01:59 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47218 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230313AbiJQKB6 (ORCPT ); Mon, 17 Oct 2022 06:01:58 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BCC0743E7A; Mon, 17 Oct 2022 03:01:57 -0700 (PDT) Received: from dggpemm500021.china.huawei.com (unknown [172.30.72.54]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4MrXZx6jBLzHvsn; Mon, 17 Oct 2022 18:01:45 +0800 (CST) Received: from dggpemm500006.china.huawei.com (7.185.36.236) by dggpemm500021.china.huawei.com (7.185.36.109) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Mon, 17 Oct 2022 18:01:33 +0800 Received: from thunder-town.china.huawei.com (10.174.178.55) by dggpemm500006.china.huawei.com (7.185.36.236) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Mon, 17 Oct 2022 18:01:32 +0800 From: Zhen Lei To: "Paul E . McKenney" , Frederic Weisbecker , Neeraj Upadhyay , "Josh Triplett" , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , , CC: Zhen Lei Subject: [PATCH 1/3] sched: Add helper kstat_cpu_softirqs_sum() Date: Mon, 17 Oct 2022 18:01:06 +0800 Message-ID: <20221017100108.2063-2-thunder.leizhen@huawei.com> X-Mailer: git-send-email 2.37.3.windows.1 In-Reply-To: <20221017100108.2063-1-thunder.leizhen@huawei.com> References: <20221017100108.2063-1-thunder.leizhen@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.174.178.55] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org Similar to kstat_cpu_irqs_sum(), it counts the sum of all software interrupts on a specified CPU. Signed-off-by: Zhen Lei --- include/linux/kernel_stat.h | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h index ddb5a358fd829f4..61d427c1962bf1c 100644 --- a/include/linux/kernel_stat.h +++ b/include/linux/kernel_stat.h @@ -67,6 +67,17 @@ static inline unsigned int kstat_softirqs_cpu(unsigned int irq, int cpu) return kstat_cpu(cpu).softirqs[irq]; } +static inline unsigned int kstat_cpu_softirqs_sum(int cpu) +{ + int i; + unsigned int sum = 0; + + for (i = 0; i < NR_SOFTIRQS; i++) + sum += kstat_softirqs_cpu(i, cpu); + + return sum; +} + /* * Number of interrupts per specific IRQ source, since bootup */ From patchwork Mon Oct 17 10:01:07 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Leizhen (ThunderTown)" X-Patchwork-Id: 13008489 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 7FEBCC4332F for ; Mon, 17 Oct 2022 10:02:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230154AbiJQKCM (ORCPT ); Mon, 17 Oct 2022 06:02:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47274 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231203AbiJQKCL (ORCPT ); Mon, 17 Oct 2022 06:02:11 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7F2892AE2C; Mon, 17 Oct 2022 03:02:09 -0700 (PDT) Received: from dggpemm500020.china.huawei.com (unknown [172.30.72.56]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4MrXXL2bxrzJn6p; Mon, 17 Oct 2022 17:59:30 +0800 (CST) Received: from dggpemm500006.china.huawei.com (7.185.36.236) by dggpemm500020.china.huawei.com (7.185.36.49) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Mon, 17 Oct 2022 18:01:34 +0800 Received: from thunder-town.china.huawei.com (10.174.178.55) by dggpemm500006.china.huawei.com (7.185.36.236) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Mon, 17 Oct 2022 18:01:33 +0800 From: Zhen Lei To: "Paul E . McKenney" , Frederic Weisbecker , Neeraj Upadhyay , "Josh Triplett" , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , , CC: Zhen Lei Subject: [PATCH 2/3] sched: Add helper nr_context_switches_cpu() Date: Mon, 17 Oct 2022 18:01:07 +0800 Message-ID: <20221017100108.2063-3-thunder.leizhen@huawei.com> X-Mailer: git-send-email 2.37.3.windows.1 In-Reply-To: <20221017100108.2063-1-thunder.leizhen@huawei.com> References: <20221017100108.2063-1-thunder.leizhen@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.174.178.55] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org Returns the number of context switches on the specified CPU, which can be used to diagnose rcu stall. Signed-off-by: Zhen Lei --- include/linux/kernel_stat.h | 1 + kernel/sched/core.c | 5 +++++ 2 files changed, 6 insertions(+) diff --git a/include/linux/kernel_stat.h b/include/linux/kernel_stat.h index 61d427c1962bf1c..ac4f9302b559c9d 100644 --- a/include/linux/kernel_stat.h +++ b/include/linux/kernel_stat.h @@ -52,6 +52,7 @@ DECLARE_PER_CPU(struct kernel_cpustat, kernel_cpustat); #define kstat_cpu(cpu) per_cpu(kstat, cpu) #define kcpustat_cpu(cpu) per_cpu(kernel_cpustat, cpu) +extern unsigned long long nr_context_switches_cpu(int cpu); extern unsigned long long nr_context_switches(void); extern unsigned int kstat_irqs_cpu(unsigned int irq, int cpu); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 5800b0623ff3068..a0d19f67f2046d9 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5229,6 +5229,11 @@ bool single_task_running(void) } EXPORT_SYMBOL(single_task_running); +unsigned long long nr_context_switches_cpu(int cpu) +{ + return cpu_rq(cpu)->nr_switches; +} + unsigned long long nr_context_switches(void) { int i; From patchwork Mon Oct 17 10:01:08 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Leizhen (ThunderTown)" X-Patchwork-Id: 13008486 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 F36FAC4332F for ; Mon, 17 Oct 2022 10:01:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230183AbiJQKB5 (ORCPT ); Mon, 17 Oct 2022 06:01:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47212 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230170AbiJQKB4 (ORCPT ); Mon, 17 Oct 2022 06:01:56 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C9C3F52087; Mon, 17 Oct 2022 03:01:53 -0700 (PDT) Received: from dggpemm500022.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4MrXZy6DZHzHw1s; Mon, 17 Oct 2022 18:01:46 +0800 (CST) Received: from dggpemm500006.china.huawei.com (7.185.36.236) by dggpemm500022.china.huawei.com (7.185.36.162) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Mon, 17 Oct 2022 18:01:34 +0800 Received: from thunder-town.china.huawei.com (10.174.178.55) by dggpemm500006.china.huawei.com (7.185.36.236) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Mon, 17 Oct 2022 18:01:34 +0800 From: Zhen Lei To: "Paul E . McKenney" , Frederic Weisbecker , Neeraj Upadhyay , "Josh Triplett" , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , , CC: Zhen Lei Subject: [PATCH 3/3] rcu: Add RCU stall diagnosis information Date: Mon, 17 Oct 2022 18:01:08 +0800 Message-ID: <20221017100108.2063-4-thunder.leizhen@huawei.com> X-Mailer: git-send-email 2.37.3.windows.1 In-Reply-To: <20221017100108.2063-1-thunder.leizhen@huawei.com> References: <20221017100108.2063-1-thunder.leizhen@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.174.178.55] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500006.china.huawei.com (7.185.36.236) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org 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. For example: rcu: INFO: rcu_preempt self-detected stall on CPU rcu: 0-....: (1250 ticks this GP) rcu: hardirqs softirqs csw/system rcu: number: 624 45 0 rcu: cputime: 69 1 2425 ==> 2500(ms) The example above shows that the number of hard and soft interrupts is small, there is zero context switching, and the system takes up a lot of time. We can quickly conclude that the current task is infinitely looped with preempt_disable(). The impact on system performance is negligible because snapshot is recorded only one time after 1/2 CPU stall timeout. Signed-off-by: Zhen Lei --- kernel/rcu/tree.h | 11 +++++++++++ kernel/rcu/tree_stall.h | 40 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 51 insertions(+) diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index d4a97e40ea9c3e2..fb3121d15cca6f8 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -158,6 +158,16 @@ union rcu_noqs { u16 s; /* Set of bits, aggregate OR here. */ }; +struct rcu_snap_record { + unsigned long gp_seq; + u64 cputime_irq; + u64 cputime_softirq; + u64 cputime_system; + unsigned int nr_hardirqs; + unsigned int nr_softirqs; + unsigned long long nr_csw; +}; + /* Per-CPU data for read-copy update. */ struct rcu_data { /* 1) quiescent-state and grace-period handling : */ @@ -262,6 +272,7 @@ struct rcu_data { short rcu_onl_gp_flags; /* ->gp_flags at last online. */ unsigned long last_fqs_resched; /* Time of last rcu_resched(). */ unsigned long last_sched_clock; /* Jiffies of last rcu_sched_clock_irq(). */ + struct rcu_snap_record snap_record; int cpu; }; diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h index 5653560573e22d6..08cfcf526f7d245 100644 --- a/kernel/rcu/tree_stall.h +++ b/kernel/rcu/tree_stall.h @@ -211,8 +211,10 @@ static void rcu_stall_kick_kthreads(void) */ static void rcu_iw_handler(struct irq_work *iwp) { + int cpu = smp_processor_id(); struct rcu_data *rdp; struct rcu_node *rnp; + struct rcu_snap_record *r; rdp = container_of(iwp, struct rcu_data, rcu_iw); rnp = rdp->mynode; @@ -222,6 +224,16 @@ static void rcu_iw_handler(struct irq_work *iwp) rdp->rcu_iw_pending = false; } raw_spin_unlock_rcu_node(rnp); + + r = &rdp->snap_record; + r->cputime_irq = kcpustat_this_cpu->cpustat[CPUTIME_IRQ]; + r->cputime_softirq = kcpustat_this_cpu->cpustat[CPUTIME_SOFTIRQ]; + r->cputime_system = kcpustat_this_cpu->cpustat[CPUTIME_SYSTEM]; + r->nr_hardirqs = kstat_cpu_irqs_sum(cpu); + r->nr_softirqs = kstat_cpu_softirqs_sum(cpu); + r->nr_csw = nr_context_switches_cpu(cpu); + barrier(); + r->gp_seq = rdp->gp_seq; } ////////////////////////////////////////////////////////////////////////////// @@ -428,6 +440,32 @@ static bool rcu_is_rcuc_kthread_starving(struct rcu_data *rdp, unsigned long *jp return j > 2 * HZ; } +static void print_cpu_stat_info(int cpu) +{ + u64 *cpustat; + unsigned long half_timeout; + struct rcu_snap_record *r; + struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); + + r = &rdp->snap_record; + if (r->gp_seq != rdp->gp_seq) + return; + + cpustat = kcpustat_this_cpu->cpustat; + half_timeout = rcu_jiffies_till_stall_check() / 2; + + pr_err(" hardirqs softirqs csw/system\n"); + pr_err(" number: %8d %10d %12lld\n", + kstat_cpu_irqs_sum(cpu) - r->nr_hardirqs, + kstat_cpu_softirqs_sum(cpu) - r->nr_softirqs, + nr_context_switches_cpu(cpu) - r->nr_csw); + pr_err("cputime: %8lld %10lld %12lld ==> %lld(ms)\n", + div_u64(cpustat[CPUTIME_IRQ] - r->cputime_irq, NSEC_PER_MSEC), + div_u64(cpustat[CPUTIME_SOFTIRQ] - r->cputime_softirq, NSEC_PER_MSEC), + div_u64(cpustat[CPUTIME_SYSTEM] - r->cputime_system, NSEC_PER_MSEC), + jiffies64_to_msecs(half_timeout)); +} + /* * Print out diagnostic information for the specified stalled CPU. * @@ -484,6 +522,8 @@ static void print_cpu_stall_info(int cpu) data_race(rcu_state.n_force_qs) - rcu_state.n_force_qs_gpstart, rcuc_starved ? buf : "", falsepositive ? " (false positive?)" : ""); + + print_cpu_stat_info(cpu); } /* Complain about starvation of grace-period kthread. */