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

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Message-ID: <245c5d4d-408c-4910-b0e1-a694a6432d88@linux.alibaba.com>
Date: Wed, 30 Oct 2024 22:54:58 +0800
From: Tianchen Ding <dtcccc@...ux.alibaba.com>
To: Peter Zijlstra <peterz@...radead.org>
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 2024/10/30 19:00, Peter Zijlstra wrote:
> 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.

Yes, "slice" is an absolute value and may not fit the hierarchical cgroup...
There probably might not be a perfect solution :(

Anyway, I'll later send v2 for the 1st patch which fixes an existing issue.

Thanks.