linux-kernel - Re: Re: [PATCH] sched/fair: remove next_buddy

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Date:   Thu, 14 Dec 2023 20:21:53 +0800
From:   Abel Wu <wuyun.abel@...edance.com>
To:     Vincent Guittot <vincent.guittot@...aro.org>,
        Wang Jinchao <wangjinchao@...sion.com>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        linux-kernel@...r.kernel.org, stone.xulei@...sion.com
Subject: Re: Re: [PATCH] sched/fair: remove next_buddy_marked

On 12/14/23 4:18 PM, Vincent Guittot Wrote:
> On Thu, 14 Dec 2023 at 06:20, Wang Jinchao <wangjinchao@...sion.com> wrote:
>>
>> Remove unused `next_buddy_marked` in `check_preempt_wakeup_fair`
>>
> 
> Fixes: 5e963f2bd465 ("sched/fair: Commit to EEVDF")

After this commit @pse preempts curr without being the NEXT_BUDDY, but
IMHO it should be, so how about this?

@@ -8259,8 +8259,11 @@ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int
         /*
          * XXX pick_eevdf(cfs_rq) != se ?
          */
-       if (pick_eevdf(cfs_rq) == pse)
+       if (pick_eevdf(cfs_rq) == pse) {
+               if (!next_buddy_marked)
+                       set_next_buddy(pse);
                 goto preempt;
+       }

         return;

which will align with before.