linux-kernel - Re: [PATCH v7 4/6] rcu: Add RCU stall diagnosis information

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Message-ID: <d4f7f41c-e1ef-606f-d700-3e67059bb06d@huawei.com>
Date:   Thu, 17 Nov 2022 09:57:18 +0800
From:   "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To:     Frederic Weisbecker <frederic@...nel.org>
CC:     "Paul E . McKenney" <paulmck@...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>, Robert Elliott <elliott@....com>
Subject: Re: [PATCH v7 4/6] rcu: Add RCU stall diagnosis information



On 2022/11/17 6:39, Frederic Weisbecker wrote:
> On Fri, Nov 11, 2022 at 09:07:07PM +0800, Zhen Lei wrote:
>> @@ -262,6 +279,8 @@ 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; /* Snapshot of core stats at half of */
>> +					    /* the first RCU stall timeout */
> 
> This should be under #ifdef CONFIG_RCU_CPU_STALL_CPUTIME

This will not work for now because we also support boot option rcupdate.rcu_cpu_stall_cputime.

> 
>> +static void print_cpu_stat_info(int cpu)
>> +{
>> +	struct rcu_snap_record rsr, *rsrp;
>> +	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);
>> +	struct kernel_cpustat *kcsp = &kcpustat_cpu(cpu);
>> +
>> +	if (!rcu_cpu_stall_cputime)
>> +		return;
>> +
>> +	rsrp = &rdp->snap_record;
>> +	if (rsrp->gp_seq != rdp->gp_seq)
>> +		return;
>> +
>> +	rsr.cputime_irq     = kcpustat_field(kcsp, CPUTIME_IRQ, cpu);
>> +	rsr.cputime_softirq = kcpustat_field(kcsp, CPUTIME_SOFTIRQ, cpu);
>> +	rsr.cputime_system  = kcpustat_field(kcsp, CPUTIME_SYSTEM, cpu);
>> +
>> +	pr_err("\t         hardirqs   softirqs   csw/system\n");
>> +	pr_err("\t number: %8ld %10d %12lld\n",
>> +		kstat_cpu_irqs_sum(cpu) - rsrp->nr_hardirqs,
>> +		kstat_cpu_softirqs_sum(cpu) - rsrp->nr_softirqs,
>> +		nr_context_switches_cpu(cpu) - rsrp->nr_csw);
>> +	pr_err("\tcputime: %8lld %10lld %12lld   ==> %lld(ms)\n",
>> +		div_u64(rsr.cputime_irq - rsrp->cputime_irq, NSEC_PER_MSEC),
>> +		div_u64(rsr.cputime_softirq - rsrp->cputime_softirq, NSEC_PER_MSEC),
>> +		div_u64(rsr.cputime_system - rsrp->cputime_system, NSEC_PER_MSEC),
>> +		jiffies64_to_msecs(jiffies - rsrp->jiffies));
> 
> jiffies_to_msecs() should be enough.

OK, thanks.

> 
> Thanks.
> 
> .
> 

-- 
Regards,
  Zhen Lei