Received-SPF: pass (google.com: domain of linux-kernel+bounces-84553-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:45e3:2400::1 as permitted sender) client-ip=2604:1380:45e3:2400::1;
Message-ID: <1606230b-83af-4f5f-b1ef-6ae8f73841f5@linux.alibaba.com>
Date: Wed, 28 Feb 2024 14:07:15 +0800
Precedence: bulk
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
From: Bitao Hu <yaoma@linux.alibaba.com>
Subject: Re: [PATCHv10 3/4] genirq: Avoid summation loops for /proc/interrupts
To: Thomas Gleixner <tglx@linutronix.de>, dianders@chromium.org,
 liusong@linux.alibaba.com, akpm@linux-foundation.org, pmladek@suse.com,
 kernelfans@gmail.com, deller@gmx.de, npiggin@gmail.com,
 tsbogend@alpha.franken.de, James.Bottomley@HansenPartnership.com,
 jan.kiszka@siemens.com
Cc: linux-kernel@vger.kernel.org, linux-mips@vger.kernel.org,
 linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
 yaoma@linux.alibaba.com
References: <20240226020939.45264-1-yaoma@linux.alibaba.com>
 <20240226020939.45264-4-yaoma@linux.alibaba.com> <87le769s0w.ffs@tglx>
 <e78357ae-7b00-446c-b010-3bd770892c9e@linux.alibaba.com>
 <87a5nlapc2.ffs@tglx>
Content-Language: en-US
In-Reply-To: <87a5nlapc2.ffs@tglx>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit

On 2024/2/27 23:39, Thomas Gleixner wrote:
> On Tue, Feb 27 2024 at 19:20, Bitao Hu wrote:
>> On 2024/2/27 17:26, Thomas Gleixner wrote:
>>>
>>> and then let kstat_irqs() and show_interrupts() use it. See?
>>
>> I have a concern. kstat_irqs() uses for_each_possible_cpu() for
>> summation. However, show_interrupts() uses for_each_online_cpu(),
>> which means it only outputs interrupt statistics for online cpus.
>> If we use for_each_possible_cpu() in show_interrupts() to calculate
>> 'any_count', there could be a problem with the following scenario:
>> If an interrupt has a count of zero on online cpus but a non-zero
>> count on possible cpus, then 'any_count' would not be zero, and the
>> statistics for that interrupt would be output, which is not the
>> desired behavior for show_interrupts(). Therefore, I think it's not
>> good to have kstat_irqs() and show_interrupts() both use the same
>> logic. What do you think?
> 
> Good point. But you simply can have
> 
> unsigned int kstat_irq_desc(struct irq_desc *desc, const struct cpumask *mask)
> 
> and hand in the appropriate cpumask, which still shares the code, no?
> 
Alright, that is a good approach.