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

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Message-ID: <a04845cf-c70a-4699-8260-27a3502fd01d@nvidia.com>
Date: Tue, 4 Mar 2025 15:32:32 +0000
From: Jon Hunter <jonathanh@...dia.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>,
 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 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>

Thanks!
Jon

-- 
nvpublic