linux-kernel - Re: [PATCH v2 3/2] sched/deadline: Check bandwidth overflow earlier for hotplug

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Message-ID: <Z4ZuaeGssJ-9RQA2@jlelli-thinkpadt14gen4.remote.csb>
Date: Tue, 14 Jan 2025 15:02:17 +0100
From: Juri Lelli <juri.lelli@...hat.com>
To: Jon Hunter <jonathanh@...dia.com>
Cc: Thierry Reding <treding@...dia.com>, Waiman Long <longman@...hat.com>,
	Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>,
	Michal Koutny <mkoutny@...e.com>, 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>,
	Phil Auld <pauld@...hat.com>, Qais Yousef <qyousef@...alina.io>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	"Joel Fernandes (Google)" <joel@...lfernandes.org>,
	Suleiman Souhlal <suleiman@...gle.com>,
	Aashish Sharma <shraash@...gle.com>,
	Shin Kawamura <kawasin@...gle.com>,
	Vineeth Remanan Pillai <vineeth@...byteword.org>,
	linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>
Subject: Re: [PATCH v2 3/2] sched/deadline: Check bandwidth overflow earlier
 for hotplug

On 14/01/25 13:52, Jon Hunter wrote:
> 
> On 13/01/2025 09:32, Juri Lelli wrote:
> > On 10/01/25 18:40, Jon Hunter wrote:
> > 
> > ...
> > 
> > > With the above I see the following ...
> > > 
> > > [   53.919672] dl_bw_manage: cpu=5 cap=3072 fair_server_bw=52428 total_bw=209712 dl_bw_cpus=4
> > > [   53.930608] dl_bw_manage: cpu=4 cap=2048 fair_server_bw=52428 total_bw=157284 dl_bw_cpus=3
> > > [   53.941601] dl_bw_manage: cpu=3 cap=1024 fair_server_bw=52428 total_bw=104856 dl_bw_cpus=2
> > 
> > So far so good.
> > 
> > > [   53.952186] dl_bw_manage: cpu=2 cap=1024 fair_server_bw=52428 total_bw=576708 dl_bw_cpus=2
> > 
> > But, this above doesn't sound right.
> > 
> > > [   53.962938] dl_bw_manage: cpu=1 cap=0 fair_server_bw=52428 total_bw=576708 dl_bw_cpus=1
> > > [   53.971068] Error taking CPU1 down: -16
> > > [   53.974912] Non-boot CPUs are not disabled
> > 
> > What is the topology of your board?
> > 
> > Are you using any cpuset configuration for partitioning CPUs?
> 
> 
> I just noticed that by default we do boot this board with 'isolcpus=1-2'. I
> see that this is a deprecated cmdline argument now and I must admit I don't
> know the history of this for this specific board. It is quite old now.
> 
> Thierry, I am curious if you have this set for Tegra186 or not? Looks like
> our BSP (r35 based) sets this by default.
> 
> I did try removing this and that does appear to fix it.

OK, good.

> Juri, let me know your thoughts.

Thanks for the additional info. I guess I could now try to repro using
isolcpus at boot on systems I have access to (to possibly understand
what the underlying problem is).

Best,
Juri