Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [RFC PATCH] sched: fix the nonsense shares when load of cfs_rq is
 too, small
To:     Vincent Guittot <vincent.guittot@linaro.org>
Cc:     Ben Segall <bsegall@google.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Mel Gorman <mgorman@suse.de>,
        "open list:SCHEDULER" <linux-kernel@vger.kernel.org>
References: <44fa1cee-08db-e4ab-e5ab-08d6fbd421d7@linux.alibaba.com>
 <20200303195245.GF2596@hirez.programming.kicks-ass.net>
 <xm26o8tc3qkv.fsf@bsegall-linux.svl.corp.google.com>
 <1180c6cd-ff61-2c9f-d689-ffe58f8c5a68@linux.alibaba.com>
 <CAKfTPtCaPz2KBmagzpEurh5S9aNFzUomHGh1pDWBx6L_29w5hw@mail.gmail.com>
From:   =?UTF-8?B?546L6LSH?= <yun.wang@linux.alibaba.com>
Message-ID: <12f79b83-491c-4b4b-0581-d23bdcec7c0c@linux.alibaba.com>
Date:   Fri, 6 Mar 2020 12:23:22 +0800
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:68.0)
 Gecko/20100101 Thunderbird/68.4.2
MIME-Version: 1.0
In-Reply-To: <CAKfTPtCaPz2KBmagzpEurh5S9aNFzUomHGh1pDWBx6L_29w5hw@mail.gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 2020/3/5 下午3:53, Vincent Guittot wrote:
> On Thu, 5 Mar 2020 at 02:14, 王贇 <yun.wang@linux.alibaba.com> wrote:
[snip]
>>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>>> index fcc968669aea..6d7a9d72d742 100644
>>> --- a/kernel/sched/fair.c
>>> +++ b/kernel/sched/fair.c
>>> @@ -3179,9 +3179,9 @@ static long calc_group_shares(struct cfs_rq *cfs_rq)
>>>         long tg_weight, tg_shares, load, shares;
>>>         struct task_group *tg = cfs_rq->tg;
>>>
>>> -       tg_shares = READ_ONCE(tg->shares);
>>> +       tg_shares = scale_load_down(READ_ONCE(tg->shares));
>>>
>>> -       load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg);
>>> +       load = max(cfs_rq->load.weight, scale_load(cfs_rq->avg.load_avg));
>>>
>>>         tg_weight = atomic_long_read(&tg->load_avg);
>>
>> Get the point, but IMHO fix scale_load_down() sounds better, to
>> cover all the similar cases, let's first try that way see if it's
>> working :-)
> 
> The problem with this solution is that the avg.load_avg of gse or
> cfs_rq might stay to 0 because it uses
> scale_load_down(se/cfs_rq->load.weight)

Will cfs_rq->load.weight be zero too without scale down?

If cfs_rq->load.weight got at least something, the load will not be
zero after pick the max, correct?

Regards,
Michael Wang

> 
>>
>> Regards,
>> Michael Wang
>>
>>>
>>>
>>>