linux-kernel - Re: [PATCH v3 4/8] sched/deadline: Rebuild root domain accounting after every update

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Message-ID: <433bb604-1490-4ac0-8e25-1b2f7464ef76@arm.com>
Date: Thu, 13 Mar 2025 10:09:34 +0100
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Juri Lelli <juri.lelli@...hat.com>
Cc: Waiman Long <llong@...hat.com>, linux-kernel@...r.kernel.org,
 cgroups@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
 Peter Zijlstra <peterz@...radead.org>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 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>, Johannes Weiner <hannes@...xchg.org>,
 Michal Koutný <mkoutny@...e.com>,
 Qais Yousef <qyousef@...alina.io>,
 Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
 Swapnil Sapkal <swapnil.sapkal@....com>,
 Shrikanth Hegde <sshegde@...ux.ibm.com>, Phil Auld <pauld@...hat.com>,
 luca.abeni@...tannapisa.it, tommaso.cucinotta@...tannapisa.it,
 Jon Hunter <jonathanh@...dia.com>
Subject: Re: [PATCH v3 4/8] sched/deadline: Rebuild root domain accounting
 after every update

On 12.03.25 17:51, Juri Lelli wrote:
> On 12/03/25 17:29, Dietmar Eggemann wrote:
>> On 12/03/2025 15:11, Juri Lelli wrote:
>>> On 12/03/25 09:55, Waiman Long wrote:
>>>> On 3/12/25 6:09 AM, Juri Lelli wrote:
>>>>> On 12/03/25 10:53, Dietmar Eggemann wrote:
>>>>>> On 11/03/2025 15:51, Waiman Long wrote:
>>
>> [...]
>>
>>>>> I unfortunately very much suspect !CPUSETS accounting is broken. But if
>>>>> that is indeed the case, it has been broken for a while. :(
>>>> Without CONFIG_CPUSETS, there will be one and only one global sched domain.
>>>> Will this still be a problem?
>>>
>>> Still need to double check. But I have a feeling we don't restore
>>> accounting correctly (at all?!) without CPUSETS. Orthogonal to this
>>> issue though, as if we don't, we didn't so far. :/
>>
>> As expected:
>>
>> Since dl_rebuild_rd_accounting() is empty with !CONFIG_CPUSETS, the same
>> issue happens.
> 
> Right, suspicion confirmed. :)
> 
> But, as I was saying, I believe it has been broken for a while/forever.
> Not only suspend/resume, the accounting itself.
> 
> Would you be OK if we address the !CPUSETS case with a separate later
> series?

Yes, we can do that.