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Date: Thu, 25 Apr 2024 12:25:16 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Yan-Jie Wang <yanjiewtw@gmail.com>
Cc: Chen Yu <yu.c.chen@intel.com>, mingo@redhat.com, juri.lelli@redhat.com,
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	wuyun.abel@bytedance.com, tglx@linutronix.de, efault@gmx.de,
	yu.chen.surf@gmail.com
Subject: Re: [RFC][PATCH 08/10] sched/fair: Implement delayed dequeue
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On Thu, Apr 11, 2024 at 09:32:23AM +0800, Yan-Jie Wang wrote:
> I have an alternative approach to delayed-dequeue inspired by the original
> CFS implementation.
> 
> The idea is to keep the task's vruntime when it goes to sleep.
> When the task is woken up, see if the lag is positive at the woken time, if
> it is the case, clamp it to 0 by setting vruntime to avg_vruntime().

Problem is that avg_vruntime() can go backwards, eg by dequeueing a
negative lag task. This gets really hard to argue about real quick.

Keeping the task competing (delaying the dequeue) is by far the simplest
solution -- conceptually.

The code just became a total mess because of cgroups :/