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Date:   Fri, 17 Nov 2023 15:34:05 +0800
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Subject: Re: [PATCH] sched/fair: Update min_vruntime for reweight_entity()
 correctly
Content-Language: en-US
From:   Abel Wu <wuyun.abel@bytedance.com>
To:     Yiwei Lin <s921975628@gmail.com>, mingo@redhat.com,
        peterz@infradead.org
Cc:     vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
        linux-kernel@vger.kernel.org
References: <20231116114217.90553-1-s921975628@gmail.com>
 <30fa2ed2-dfee-4dbf-bb44-1b0374877706@bytedance.com>
In-Reply-To: <30fa2ed2-dfee-4dbf-bb44-1b0374877706@bytedance.com>
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On 11/16/23 7:52 PM, Abel Wu Wrote:
> Please add a Fix tag like this:
> 
> Fixes: eab03c23c2a1 ("sched/eevdf: Fix vruntime adjustment on reweight")

Can you resend this patch with this fix tag please?

> 
> On 11/16/23 7:42 PM, Yiwei Lin Wrote:
>> Since reweight_entity() may have chance to change the weight of
>> cfs_rq->curr entity, we should also update_min_vruntime() if
>> this is the case
>>
>> Signed-off-by: Yiwei Lin <s921975628@gmail.com>
>> ---
>>   kernel/sched/fair.c | 20 ++++++++++----------
>>   1 file changed, 10 insertions(+), 10 deletions(-)
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 07f555857..6fb89f4a3 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -3815,17 +3815,17 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
>>       enqueue_load_avg(cfs_rq, se);
>>       if (se->on_rq) {
>>           update_load_add(&cfs_rq->load, se->load.weight);
>> -        if (!curr) {
>> -            /*
>> -             * The entity's vruntime has been adjusted, so let's check
>> -             * whether the rq-wide min_vruntime needs updated too. Since
>> -             * the calculations above require stable min_vruntime rather
>> -             * than up-to-date one, we do the update at the end of the
>> -             * reweight process.
>> -             */
>> +        if (!curr)
>>               __enqueue_entity(cfs_rq, se);
>> -            update_min_vruntime(cfs_rq);
>> -        }
>> +
>> +        /*
>> +         * The entity's vruntime has been adjusted, so let's check
>> +         * whether the rq-wide min_vruntime needs updated too. Since
>> +         * the calculations above require stable min_vruntime rather
>> +         * than up-to-date one, we do the update at the end of the
>> +         * reweight process.
>> +         */
>> +        update_min_vruntime(cfs_rq);
>>       }
>>   }
> 
> LGTM, thanks!