linux-kernel - Re: [PATCH v5 3/4] sched: Add helper nr_context_switches

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Date:   Tue, 8 Nov 2022 20:03:57 +0530
From:   Mukesh Ojha <quic_mojha@...cinc.com>
To:     Zhen Lei <thunder.leizhen@...wei.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        "Neeraj Upadhyay" <quic_neeraju@...cinc.com>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Joel Fernandes <joel@...lfernandes.org>, <rcu@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Robert Elliott <elliott@....com>
Subject: Re: [PATCH v5 3/4] sched: Add helper nr_context_switches_cpu()

Hi,

On 11/4/2022 7:41 PM, Zhen Lei wrote:
> Returns the number of context switches on the specified CPU, which can be
> used to diagnose rcu stall.
> 
> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com> > ---
>   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 898076e173a928a..9935f7ecbfb9e31 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;

LGTM.
Reviewed-by: Mukesh Ojha <quic_mojha@...cinc.com>

-Mukesh