Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <1595250506-9769-1-git-send-email-qianjun.kernel@gmail.com> <87eep32zod.fsf@nanos.tec.linutronix.de>
In-Reply-To: <87eep32zod.fsf@nanos.tec.linutronix.de>
From:   jun qian <qianjun.kernel@gmail.com>
Date:   Thu, 23 Jul 2020 12:48:17 +0800
Message-ID: <CAKc596LR-=yabCEo_PT0p6Ynr5EWEXc1Fq+CcpPMeo9t3ALV9Q@mail.gmail.com>
Subject: Re: [RFC PATCH v2] Softirq:avoid large sched delay from the pending softirqs
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     peterz@infradead.org, will@kernel.org, luto@kernel.org,
        linux-kernel@vger.kernel.org, Uladzislau Rezki <urezki@gmail.com>,
        Yafang Shao <laoar.shao@gmail.com>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Thu, Jul 23, 2020 at 2:05 AM Thomas Gleixner <tglx@linutronix.de> wrote:
>
> qianjun.kernel@gmail.com writes:
> > +
> > +             end =3D ktime_get();
> > +             delta =3D ktime_to_us(end - start);
>
> What's the point of this conversion? That's a division for no value
> because you can simply define the maximum time in nanoseconds with the
> same effect, i.e.
>
>         ktime_t end =3D ktime_get() + MAX_SOFTIRQ_TIME_NS;
>
>         if (need_resched() && ktime_get() > end)
>                 break;
>
> So you can spare all that start, delta and conversion dance and keep the
> code simple.
>
> Also notice that need_resched() wants to be evaluated first because
> there is no point to do the more expensive time read if need_resched()
> is false.
good suggestion=EF=BC=8CThanks

I will make changes in the next version
>
> Thanks,
>
>         tglx