linux-kernel - Re: [PATCH v4 0/8] Fix SCHED_DEADLINE bandwidth accounting during suspend

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Message-ID: <92a9cb8f-761a-4cc6-82f9-ea66aeecddfe@arm.com>
Date: Mon, 17 Mar 2025 09:39:04 +0100
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Juri Lelli <juri.lelli@...hat.com>, linux-kernel@...r.kernel.org,
 cgroups@...r.kernel.org
Cc: 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>,
 Waiman Long <longman@...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 v4 0/8] Fix SCHED_DEADLINE bandwidth accounting during
 suspend

On 13/03/2025 18:00, Juri Lelli wrote:
> Hello!
> 
> Jon reported [1] a suspend regression on a Tegra board configured to
> boot with isolcpus and bisected it to commit 53916d5fd3c0
> ("sched/deadline: Check bandwidth overflow earlier for hotplug").
> 
> Root cause analysis pointed out that we are currently failing to
> correctly clear and restore bandwidth accounting on root domains after
> changes that initiate from partition_sched_domains(), as it is the case
> for suspend operations on that board.
> 
> This is v4 [2] of the proposed approach to fix the issue. With respect
> to v3 only patch 04 has changed as I have added the wrappers Waiman
> created to make sure we always call partition_sched_domains() while
> holding cpuset_mutex (issue pointed out by Dietmar on v3).
> 
> Dietmar also pointed out that the issue at hand is not fixed by this set
> for !CONFIG_CPUSETS configuration. But, given the fact that bandwidth
> accounting has been broken for such configuration so far (sigh) and that
> the vast majority (if not all) distributions have CPUSETS enabled, we
> decided to leave fixing the remaining issue for later. I will soon try
> to find time to keep looking into it.

Reviewed-by: Dietmar Eggemann <dietmar.eggemann@....com>

Tested-by: Dietmar Eggemann <dietmar.eggemann@....com>

Testcase: suspend/resume

on Arm64 big.LITTLE cpumask=[LITTLE][big]=[0,3-5][1-2]
plus cmd line option 'isolcpus=3,4'.