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

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Message-ID: <5bb31903-207c-2171-5914-ec3046f7241b@huawei.com>
Date:   Mon, 14 Nov 2022 22:26:40 +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 2/6] sched: Add helper kstat_cpu_softirqs_sum()



On 2022/11/14 20:50, Frederic Weisbecker wrote:
> 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...

Yes, this was discussed before. In fact, I think unsigned int and unsigned
long are all right.

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

-- 
Regards,
  Zhen Lei