linux-kernel - Re: [PATCH] sched/fair: fix pick_eevdf to always find the correct se

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Date:   Fri, 6 Oct 2023 21:24:45 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Mike Galbraith <efault@....de>
Cc:     Marek Szyprowski <m.szyprowski@...sung.com>,
        Biju Das <biju.das.jz@...renesas.com>,
        "bsegall@...gle.com" <bsegall@...gle.com>,
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        "corbet@....net" <corbet@....net>,
        "dietmar.eggemann@....com" <dietmar.eggemann@....com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "joel@...lfernandes.org" <joel@...lfernandes.org>,
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        <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH] sched/fair: fix pick_eevdf to always find the correct se

On Fri, Oct 06, 2023 at 05:55:01PM +0200, Peter Zijlstra wrote:

> And yeah, min_deadline is hosed somehow.
> 
> migration/28-185     [028] d..2.    70.264274: validate_cfs_rq: --- /
> migration/28-185     [028] d..2.    70.264277: __print_se: ffff88845cf48080 w: 1024 ve: -58857638 lag: 870381 vd: -55861854 vmd: -66302085 E (11372/tr)
> migration/28-185     [028] d..2.    70.264280: __print_se:   ffff88810d165800 w: 25 ve: -80323686 lag: 22336429 vd: -41496434 vmd: -66302085 E (-1//autogroup-31)
> migration/28-185     [028] d..2.    70.264282: __print_se:   ffff888108379000 w: 25 ve: 0 lag: -57987257 vd: 114632828 vmd: 114632828 N (-1//autogroup-33)
> migration/28-185     [028] d..2.    70.264283: validate_cfs_rq: min_deadline: -55861854 avg_vruntime: -62278313462 / 1074 = -57987256
> 
> I need to go make dinner (kids hungry), but I'll see if I can figure out
> how this happens...

*sigh*, does the below help?

---
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 04fbcbda97d5..6a670f119efa 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3632,6 +3747,7 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
 		 */
 		deadline = div_s64(deadline * old_weight, weight);
 		se->deadline = se->vruntime + deadline;
+		min_deadline_cb_propagate(&se->run_node, NULL);
 	}
 
 #ifdef CONFIG_SMP