linux-kernel - Re: [PATCH 0/5] Fix SCHED_DEADLINE bandwidth accounting during suspend

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Message-ID: <Z8ciDMdstzJCZoBm@jlelli-thinkpadt14gen4.remote.csb>
Date: Tue, 4 Mar 2025 15:53:48 +0000
From: Juri Lelli <juri.lelli@...hat.com>
To: Jon Hunter <jonathanh@...dia.com>
Cc: 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>,
	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>,
	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,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH 0/5] Fix SCHED_DEADLINE bandwidth accounting during
 suspend

Hi Jon,

On 04/03/25 15:32, Jon Hunter wrote:
> Hi Juri,
> 
> On 04/03/2025 08:40, 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.
> > 
> > The way we currently make sure that accounting properly follows root
> > domain changes is quite convoluted and was indeed missing some corner
> > cases. So, instead of adding yet more fragile operations, I thought we
> > could simplify things by always clearing and rebuilding bandwidth
> > information on all domains after an update is complete. Also, we should
> > be ignoring DEADLINE special tasks when doing so (e.g. sugov), since we
> > ignore them already for runtime enforcement and admission control
> > anyway.
> > 
> > The following implements the approach by:
> > 
> > - 01/05: filter out DEADLINE special tasks
> > - 02/05: preparatory wrappers to be able to grab sched_domains_mutex on
> >           UP
> > - 03/05: generalize unique visiting of root domains so that we can
> >           re-use the mechanism elsewhere
> > - 04/05: the bulk of the approach, clean and rebuild after changes
> > - 05/05: clean up a now redundant call
> > 
> > Please test and review. The set is also available at
> > 
> > git@...hub.com:jlelli/linux.git upstream/deadline/domains-suspend
> 
> 
> I know that this is still under review, but I have tested on my side and it
> is working for me, so feel free to include my ...
> 
> Tested-by: Jon Hunter <jonathanh@...dia.com>

Great to hear this and thanks for the super quick turn around with
testing. I will be implementing the changes that Waiman (and possibly
others) is suggesting and post a new version soon.

Best,
Juri