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Date:   Wed, 4 Mar 2020 10:52:09 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Vincent Guittot <vincent.guittot@linaro.org>
Cc:     =?utf-8?B?546L6LSH?= <yun.wang@linux.alibaba.com>,
        Ingo Molnar <mingo@redhat.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
        "open list:SCHEDULER" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH] sched: fix the nonsense shares when load of cfs_rq
 is too, small
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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.