linux-kernel - Re: [PATCH] cgroup/cpuset: Disable cpuset_cpumask_can

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Message-ID: <1515c439-32ef-4aee-9f69-c5af1fca79e3@redhat.com>
Date: Fri, 15 Nov 2024 12:55:49 -0500
From: Waiman Long <llong@...hat.com>
To: Juri Lelli <juri.lelli@...hat.com>
Cc: Tejun Heo <tj@...nel.org>, Johannes Weiner <hannes@...xchg.org>,
 Michal Koutný <mkoutny@...e.com>, cgroups@...r.kernel.org,
 linux-kernel@...r.kernel.org, Phil Auld <pauld@...hat.com>
Subject: Re: [PATCH] cgroup/cpuset: Disable cpuset_cpumask_can_shrink() test
 if not load balancing

On 11/15/24 5:54 AM, Juri Lelli wrote:
> Hi Waiman,
>
> On 14/11/24 13:19, Waiman Long wrote:
>> With some recent proposed changes [1] in the deadline server code,
>> it has caused a test failure in test_cpuset_prs.sh when a change
>> is being made to an isolated partition. This is due to failing
>> the cpuset_cpumask_can_shrink() check for SCHED_DEADLINE tasks at
>> validate_change().
> What sort of change is being made to that isolated partition? Which test
> is failing from the test_cpuset_prs.sh collection? Asking because I now
> see "All tests PASSED" running that locally (with all my 3 patches on
> top of cgroup/for-6.13 w/o this last patch from you).

The failing test isn't an isolated partition. The actual test failure is

Test TEST_MATRIX[62] failed result check!
C0-4:X2-4:S+ C1-4:X2-4:S+:P2 C2-4:X4:P1 . . X5 . . 0 
A1:0-4,A2:1-4,A3:2-4 A1:P0,A2:P-2,A3:P-1

In this particular case, cgroup A3 has the following setting before the 
X5 operation.

A1/A2/A3/cpuset.cpus: 2-4
A1/A2/A3/cpuset.cpus.exclusive: 4
A1/A2/A3/cpuset.cpus.effective: 4
A1/A2/A3/cpuset.cpus.exclusive.effective: 4
A1/A2/A3/cpuset.cpus.partition: root

I believe this is fixed by my other change in the commit to change 
arguments of cpuset_cpumask_can_shrink() to use effective_cpus instead 
as cpus_allowed may not represent what CPUs are currently used in the 
partition.

Cheers,
Longman