linux-kernel - Re: [PATCH v3 4/8] sched/deadline: Rebuild root domain accounting after every update

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Message-ID: <78bc0eda-7471-404d-a816-bd5f1a8d4b27@arm.com>
Date: Wed, 12 Mar 2025 17:29:39 +0100
From: Dietmar Eggemann <dietmar.eggemann@....com>
To: Juri Lelli <juri.lelli@...hat.com>, Waiman Long <llong@...hat.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>,
 Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
 Mel Gorman <mgorman@...e.de>, Valentin Schneider <vschneid@...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 v3 4/8] sched/deadline: Rebuild root domain accounting
 after every update

On 12/03/2025 15:11, Juri Lelli wrote:
> On 12/03/25 09:55, Waiman Long wrote:
>> On 3/12/25 6:09 AM, Juri Lelli wrote:
>>> On 12/03/25 10:53, Dietmar Eggemann wrote:
>>>> On 11/03/2025 15:51, Waiman Long wrote:

[...]

>>> I unfortunately very much suspect !CPUSETS accounting is broken. But if
>>> that is indeed the case, it has been broken for a while. :(
>> Without CONFIG_CPUSETS, there will be one and only one global sched domain.
>> Will this still be a problem?
> 
> Still need to double check. But I have a feeling we don't restore
> accounting correctly (at all?!) without CPUSETS. Orthogonal to this
> issue though, as if we don't, we didn't so far. :/

As expected:

Since dl_rebuild_rd_accounting() is empty with !CONFIG_CPUSETS, the same
issue happens.

Testcase: suspend/resume

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

...

[ 2250.898771] PM: suspend entry (deep)
[ 2250.902566] Filesystems sync: 0.000 seconds
[ 2250.908704] Freezing user space processes
[ 2250.914379] Freezing user space processes completed (elapsed 0.001
seconds)
[ 2250.921433] OOM killer disabled.
[ 2250.924702] Freezing remaining freezable tasks
[ 2250.930497] Freezing remaining freezable tasks completed (elapsed
0.001 seconds)
...
[ 2251.060052] Disabling non-boot CPUs ...
[ 2251.060426] CPU0 attaching NULL sched-domain.
[ 2251.060455] CPU1 attaching NULL sched-domain.
[ 2251.060478] CPU2 attaching NULL sched-domain.
[ 2251.060499] CPU5 attaching NULL sched-domain.
[ 2251.060712] CPU0 attaching sched-domain(s):
[ 2251.060723]  domain-0: span=0-2 level=PKG
[ 2251.060750]   groups: 0:{ span=0 cap=503 }, 1:{ span=1-2 cap=2048 }
[ 2251.060829] CPU1 attaching sched-domain(s):
[ 2251.060838]  domain-0: span=1-2 level=MC
[ 2251.060859]   groups: 1:{ span=1 }, 2:{ span=2 }
[ 2251.060906]   domain-1: span=0-2 level=PKG
[ 2251.060926]    groups: 1:{ span=1-2 cap=2048 }, 0:{ span=0 cap=503 }
[ 2251.061000] CPU2 attaching sched-domain(s):
[ 2251.061009]  domain-0: span=1-2 level=MC
[ 2251.061030]   groups: 2:{ span=2 }, 1:{ span=1 }
[ 2251.061077]   domain-1: span=0-2 level=PKG
[ 2251.061097]    groups: 1:{ span=1-2 cap=2048 }, 0:{ span=0 cap=503 }
[ 2251.061221] root domain span: 0-2
[ 2251.061270] root_domain 0-2: pd1:{ cpus=1-2 nr_pstate=5 } pd0:{
cpus=0,3-5 nr_pstate=5 }
[ 2251.064976] psci: CPU5 killed (polled 0 ms)
[ 2251.066211] Error taking CPU4 down: -16
[ 2251.066226] Non-boot CPUs are not disabled
[ 2251.066234] Enabling non-boot CPUs ...

[...]