linux-kernel - Re: [PATCH v7 2/6] sched: Add helper kstat_cpu_softirqs

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Message-ID: <20221114125018.GF590078@lothringen>
Date:   Mon, 14 Nov 2022 13:50:18 +0100
From:   Frederic Weisbecker <frederic@...nel.org>
To:     "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
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 2/6] sched: Add helper kstat_cpu_softirqs_sum()

On Mon, Nov 14, 2022 at 08:45:26PM +0800, Leizhen (ThunderTown) wrote:
> 
> 
> On 2022/11/14 19:42, Frederic Weisbecker wrote:
> > On Fri, Nov 11, 2022 at 09:07:05PM +0800, Zhen Lei wrote:
> >> Similar to kstat_cpu_irqs_sum(), it counts the sum of all software
> >> interrupts on a specified CPU.
> >>
> >> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
> >> ---
> >>  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 90e2fdc17d79ff8..898076e173a928a 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);
> > 
> > This should return a u64 or at least an unsigned long so that high
> > numbers of CPUs don't overflow easily.
> 
> OK! Then I'll adjust the following types by the way.
> 
> struct kernel_stat {
>         unsigned long irqs_sum;
>         unsigned int softirqs[NR_SOFTIRQS];
> };
> 
> static inline unsigned int kstat_softirqs_cpu(unsigned int irq, int cpu)

And I also misread kstat_softirqs_cpu() content, my bad. Although at some point
the sum of all softirqs within a single CPU might overflow in an int so I guess
that still applies...

Thanks.


> 
> 
> 
> 
> > 
> > Thanks.
> > 
> >> +
> >> +	return sum;
> >> +}
> >> +
> >>  /*
> >>   * Number of interrupts per specific IRQ source, since bootup
> >>   */
> >> -- 
> >> 2.25.1
> >>
> > .
> > 
> 
> -- 
> Regards,
>   Zhen Lei