linux-kernel - Re:Re: [PATCH,RESEND] softirq: Introduce SOFTIRQ_FORCED

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Message-ID: <AJEACAC1D27qN9TVG8Nujqqw.3.1629700439268.Hmail.wangqing@vivo.com>
Date:   Mon, 23 Aug 2021 14:33:59 +0800 (GMT+08:00)
From:   王擎 <wangqing@...o.com>
To:     Mike Galbraith <efault@....de>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Michal Hocko <mhocko@...nel.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        Will Deacon <will@...nel.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Dirk Behme <dirk.behme@...bosch.com>,
        linux-kernel@...r.kernel.org
Subject: Re:Re: [PATCH,RESEND] softirq: Introduce SOFTIRQ_FORCED_THREADING


>On Mon, 2021-08-23 at 11:33 +0800, Wang Qing wrote:
>> At present, whether the softirq is executed when the interrupt exits
>> is controlled by IRQ_FORCED_THREADING. This is unreasonable. It should
>> be split and allowed to take effect separately.
>
>Decades long practice suddenly became "unreasonable"?  I think not.  

"unreasonable" may be my misnomer, but it is really necessary to separate
softirq from IRQ_FORCED_THREADING, which can be effective separately.

>
>Trying to carve out bits and pieces of RT to merge immediately isn't
>likely to make the ongoing merge effort go anyfaster or smoother.

I am not trying to carve out bits and pieces of RT, but I encountered actual
problems in my project. For example, in Android, we will not enable 
IRQ_FORCED_THREADING, Android is not a high real-time requirements, 
but in some scenariossome, RT processes cannot be scheduled in time
and the frame is dropped due to the execution time of softirq is too long,
also some softirq cannot be executed in time in ksoftirqs, and delays occur, 
such as IO.

Therefore, why not give the user a choice to balance the execution of softirq
while not enable IRQ_FORCED_THREADING, so as to meet the inconsistent 
scenes and needs

Thanks.
Qing
>
>	Just my $.02,
>
>	-Mike
>
>