linux-kernel - Re: [PATCH 3/4] sched/fair: introduce core_vruntime and core_min

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Message-ID: <20231115122027.GZ8262@noisy.programming.kicks-ass.net>
Date:   Wed, 15 Nov 2023 13:20:27 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Cruz Zhao <CruzZhao@...ux.alibaba.com>
Cc:     mingo@...hat.com, juri.lelli@...hat.com,
        vincent.guittot@...aro.org, dietmar.eggemann@....com,
        rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
        bristot@...hat.com, vschneid@...hat.com, joel@...lfernandes.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] sched/fair: introduce core_vruntime and
 core_min_vruntime

On Wed, Nov 15, 2023 at 07:33:40PM +0800, Cruz Zhao wrote:
> To compare the priority of sched_entity from different cpus of a core,
> we introduce core_vruntime to struct sched_entity and core_min_vruntime
> to struct cfs_rq.
> 
> cfs_rq->core->core_min_vruntime records the min vruntime of the cfs_rqs
> of the same task_group among the core, and se->core_vruntime is the
> vruntime relative to se->cfs_rq->core->core_min_vruntime.

But that makes absolutely no sense. vruntime of different RQs can
advance at wildly different rates. Not to mention there's this random
offset between them.

No, this cannot be.