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Subject: Re: [RFC PATCH] sched: fix the nonsense shares when load of cfs_rq is
 too, small
To:     Peter Zijlstra <peterz@infradead.org>,
        Vincent Guittot <vincent.guittot@linaro.org>
Cc:     Ingo Molnar <mingo@redhat.com>, Juri Lelli <juri.lelli@redhat.com>,
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        Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
        "open list:SCHEDULER" <linux-kernel@vger.kernel.org>
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Date:   Thu, 5 Mar 2020 09:08:10 +0800
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On 2020/3/4 下午5:52, Peter Zijlstra wrote:
> On Wed, Mar 04, 2020 at 09:47:34AM +0100, Vincent Guittot wrote:
>> you will add +1 of nice prio for each device
>>
>> should we use instead
>> # define scale_load_down(w) ((w >> SCHED_FIXEDPOINT_SHIFT) ? (w >>
>> SCHED_FIXEDPOINT_SHIFT) : MIN_SHARES)
> 
> That's '((w >> SHIFT) ?: MIN_SHARES)', but even that is not quite right.
> 
> I think we want something like:
> 
> #define scale_load_down(w) \
> ({ unsigned long ___w = (w); \
>    if (___w) \
>      ____w = max(MIN_SHARES, ___w >> SHIFT); \
>    ___w; })
> 
> That is, we very much want to retain 0 I'm thinking.

Should works, I'll give this one a test and send another fix :-)

Regards,
Michael Wang

>