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

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Message-ID: <fc780143-2f2f-4b2d-9737-fb64bc8306b2@nvidia.com>
Date: Mon, 13 Jan 2025 13:53:20 +0000
From: Jon Hunter <jonathanh@...dia.com>
To: Juri Lelli <juri.lelli@...hat.com>
Cc: 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 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?

This is a Tegra186 and the topology is described in 
arch/arm64/boot/dts/nvidia/tegra186.dtsi. This is from the datasheet ...

"Two CPU clusters connected by a high-performance coherent interconnect 
fabric designed by NVIDIA; enables simultaneous operation of both CPU 
clusters for a true heterogeneous multi-processing (HMP) environment. 
The Denver 2 (Dual-Core) CPU clusters is optimized for higher 
single-thread performance; the ARM Cortex-A57 MPCore (Quad-Core) CPU 
clusters is better suited for multi-threaded applications and lighter 
loads."

So one of these ARM big.LITTLE style topologies.

> Are you using any cpuset configuration for partitioning CPUs?

Not that I am aware of.

> Also, could you please add sched_debug to the kernel cmdline and enable
> CONFIG_SCHED_DEBUG (if not enabled already)? That should print
> additional information about scheduling domains in case they get
> reconfigured for some reason.

OK I can enable that.

Thanks
Jon

-- 
nvpublic