linux-kernel - Re: [RFC PATCH 2/2] sched/eevdf: Introduce a cgroup interface for slice

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Message-ID: <20241030110056.GL14555@noisy.programming.kicks-ass.net>
Date: Wed, 30 Oct 2024 12:00:56 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Tianchen Ding <dtcccc@...ux.alibaba.com>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>, Tejun Heo <tj@...nel.org>
Subject: Re: [RFC PATCH 2/2] sched/eevdf: Introduce a cgroup interface for
 slice

On Mon, Oct 28, 2024 at 02:33:13PM +0800, Tianchen Ding wrote:
> Introduce "cpu.fair_slice" for cgroup v2 and "cpu.fair_slice_us" for v1
> according to their name styles. The unit is always microseconds.
> 
> A cgroup with shorter slice can preempt others more easily. This could be
> useful in container scenarios.
> 
> By default, cpu.fair_slice is 0, which means the slice of se is
> calculated by min_slice from its cfs_rq. If cpu.fair_slice is set, it
> will overwrite se->slice with the customized value.

So I'm not sure I like to expose this, like this.

The thing is, this is really specific to the way we schedule the cgroup
mess, fully hierarchical. If you want to collapse all this, like one of
those bpf schedulers does, then you cannot do this.