linux-kernel - Re: [PATCH-cgroup v5 0/5] cgroup/cpuset: Support remote partitions

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Date:   Tue, 25 Jul 2023 16:49:51 -0400
From:   Waiman Long <longman@...hat.com>
To:     Tejun Heo <tj@...nel.org>, Zefan Li <lizefan.x@...edance.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Christian Brauner <brauner@...nel.org>,
        Jonathan Corbet <corbet@....net>, Shuah Khan <shuah@...nel.org>
Cc:     cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        Juri Lelli <juri.lelli@...hat.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Michal Koutný <mkoutny@...e.com>,
        Giuseppe Scrivano <gscrivan@...hat.com>
Subject: Re: [PATCH-cgroup v5 0/5] cgroup/cpuset: Support remote partitions


On 7/13/23 13:25, Waiman Long wrote:
>   v5:
>    - [v4] https://lore.kernel.org/lkml/20230627143508.1576882-1-longman@redhat.com/
>    - Drop the first 4 patches as they had been merged.
>    - Make cpuset.cpus.exclusive invariant once it is manually set. This
>      also means the cpuset.cpus.exclusive may not show the effective value
>      that is actually being used.
>    - Update the documentation and test accordingly.
>
>   v4:
>    - [v3] https://lore.kernel.org/lkml/20230627005529.1564984-1-longman@redhat.com/
>    - Fix compilation problem reported by kernel test robot.
>
> This patch series introduces a new cpuset control file
> "cpuset.cpus.exclusive" which must be a subset of "cpuset.cpus"
> and the parent's "cpuset.cpus.exclusive". This control file lists
> the exclusive CPUs to be distributed down the hierarchy. Any one
> of the exclusive CPUs can only be distributed to at most one child
> cpuset. Unlike "cpuset.cpus", invalid input to "cpuset.cpus.exclusive"
> will be rejected with an error. This new control file has no effect on
> the behavior of the cpuset until it turns into a partition root. At that
> point, its effective CPUs will be set to its exclusive CPUs unless some
> of them are offline.
>
> This patch series also introduces a new category of cpuset partition
> called remote partitions. The existing partition category where the
> partition roots have to be clustered around the root cgroup in a
> hierarchical way is now referred to as local partitions.
>
> A remote partition can be formed far from the root cgroup
> with no partition root parent. While local partitions can be
> created without touching "cpuset.cpus.exclusive" as it can be set
> automatically if a cpuset becomes a local partition root. Properly set
> "cpuset.cpus.exclusive" values down the hierarchy are required to create
> a remote partition.
>
> Both scheduling and isolated partitions can be formed in a remote
> partition. A local partition can be created under a remote partition.
> A remote partition, however, cannot be formed under a local partition
> for now.
>
> Modern container orchestration tools like Kubernetes use the cgroup
> hierarchy to manage different containers. And it is relying on other
> middleware like systemd to help managing it. If a container needs to
> use isolated CPUs, it is hard to get those with the local partitions
> as it will require the administrative parent cgroup to be a partition
> root too which tool like systemd may not be ready to manage.
>
> With this patch series, we allow the creation of remote partition
> far from the root. The container management tool can manage the
> "cpuset.cpus.exclusive" file without impacting the other cpuset
> files that are managed by other middlewares. Of course, invalid
> "cpuset.cpus.exclusive" values will be rejected.
>
> Waiman Long (5):
>    cgroup/cpuset: Add cpuset.cpus.exclusive for v2
>    cgroup/cpuset: Introduce remote partition
>    cgroup/cpuset: Check partition conflict with housekeeping setup
>    cgroup/cpuset: Documentation update for partition
>    cgroup/cpuset: Extend test_cpuset_prs.sh to test remote partition
>
>   Documentation/admin-guide/cgroup-v2.rst       |  114 +-
>   kernel/cgroup/cpuset.c                        | 1242 ++++++++++++-----
>   .../selftests/cgroup/test_cpuset_prs.sh       |  419 ++++--
>   3 files changed, 1291 insertions(+), 484 deletions(-)
>
Tejun,

Do you have any further suggested change that you would like to see?

Cheers,
Longman