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Subject: Re: [PATCH 2/4] sched/fair: Move avg_scan_cost calculations under
 SIS_PROP
To:     Mel Gorman <mgorman@techsingularity.net>
Cc:     Vincent Guittot <vincent.guittot@linaro.org>,
        Peter Ziljstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Barry Song <song.bao.hua@hisilicon.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Valentin Schneider <valentin.schneider@arm.com>,
        Linux-ARM <linux-arm-kernel@lists.infradead.org>
References: <20201208153501.1467-1-mgorman@techsingularity.net>
 <20201208153501.1467-3-mgorman@techsingularity.net>
 <CAKfTPtBGghbKimO17UTPUHQGZc=GkY849HFrkqqojirPhJKFoQ@mail.gmail.com>
 <3255625e-fa92-dc09-9fab-5621122f4af0@linux.intel.com>
 <20201209090507.GM3371@techsingularity.net>
From:   "Li, Aubrey" <aubrey.li@linux.intel.com>
Message-ID: <14963d1e-02ea-c298-d6b4-2db637913ee3@linux.intel.com>
Date:   Wed, 9 Dec 2020 19:07:11 +0800
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On 2020/12/9 17:05, Mel Gorman wrote:
> On Wed, Dec 09, 2020 at 01:28:11PM +0800, Li, Aubrey wrote:
>>>>                         nr = div_u64(span_avg, avg_cost);
>>>>                 else
>>>>                         nr = 4;
>>>> -       }
>>>> -
>>>> -       time = cpu_clock(this);
>>>>
>>>> -       cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr);
>>>> +               time = cpu_clock(this);
>>>> +       }
>>>>
>>>>         for_each_cpu_wrap(cpu, cpus, target) {
>>>>                 if (!--nr)
>>
>> nr is the key of this throttling mechanism, need to be placed under sched_feat(SIS_PROP) as well.
>>
> 
> It isn't necessary as nr in initialised to INT_MAX if !SIS_PROP.
>If !SIS_PROP, nr need to -1 then tested in the loop, instead of testing directly.
But with SIS_PROP, need adding a test in the loop.
Since SIS_PROP is default true, I think it's okay to keep the current way.

Thanks,
-Aubrey