linux-kernel - Re: [PATCH -next RFC 00/16] cpuset: rework local partition logic

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Message-ID: <8a6a99e8-f171-4f1a-86db-21ecd3cd2287@redhat.com>
Date: Sun, 28 Sep 2025 12:00:37 -0400
From: Waiman Long <llong@...hat.com>
To: Chen Ridong <chenridong@...weicloud.com>, tj@...nel.org,
 hannes@...xchg.org, mkoutny@...e.com
Cc: cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
 lujialin4@...wei.com, chenridong@...wei.com
Subject: Re: [PATCH -next RFC 00/16] cpuset: rework local partition logic

On 9/28/25 3:12 AM, Chen Ridong wrote:
> From: Chen Ridong <chenridong@...wei.com>
>
> The current local partition implementation consolidates all operations
> (enable, disable, invalidate, and update) within the large
> update_parent_effective_cpumask() function, which exceeds 300 lines.
> This monolithic approach has become increasingly difficult to understand
> and maintain. Additionally, partition-related fields are updated in
> multiple locations, leading to redundant code and potential corner case
> oversights.
>
> This patch series refactors the local partition logic by separating
> operations into dedicated functions: local_partition_enable(),
> local_partition_disable(), and local_partition_update(), creating
> symmetry with the existing remote partition infrastructure.
>
> The series is organized as follows:
>
> 1. Infrastructure Preparation (Patches 1-2):
>     - Code cleanup and preparation for the refactoring work
>
> 2. Core Partition Operations (Patches 3-5):
>     - Factor out partition_enable(), partition_disable(), and
>       partition_update() functions from remote partition operations
>
> 3. Local Partition Implementation (Patches 6-9):
>     - Separate update_parent_effective_cpumask() into dedicated functions:
>       * local_partition_enable()
>       * local_partition_disable()
>       * local_partition_invalidate()
>       * local_partition_update()
>
> 4. Optimization and Cleanup (Patches 10-16):
>     - Remove redundant partition-related operations
>     - Additional optimizations based on the new architecture
>
> Key improvements:
> - Centralized management of partition-related fields (partition_root_state,
>    prs_err, nr_subparts, remote_sibling, effective_xcpus) within the
>    partition_enable/disable/update functions
> - Consistent operation patterns for both local and remote partitions
>    with type-specific validation checks
> - Fixed bug where isolcpus remained in root partition after isolated
>    partition transitioned to root

You are really active in restructuring the cpuset code. However, the 
next merge window for v6.18 is going to open later today or tomorrow. I 
will start reviewing this patch series once the merge window closes 2 
weeks later.

Cheers,
Longman

> Chen Ridong (16):
>    cpuset: use update_partition_sd_lb in update_cpumasks_hier
>    cpuset: generalize validate_partition() interface
>    cpuset: factor out partition_enable() function
>    cpuset: factor out partition_disable() function
>    cpuset: factor out partition_update() function
>    cpuset: introduce local_partition_enable()
>    cpuset: introduce local_partition_disable()
>    cpuset: introduce local_partition_invalidate()
>    cpuset: introduce local_partition_update()
>    cpuset: remove redundant partition field updates
>    cpuset: simplify partition update logic for hotplug tasks
>    cpuset: unify local partition disable and invalidate
>    cpuset: use partition_disable for compute_partition_effective_cpumask
>    cpuset: fix isolcpus stay in root when isolated partition changes to
>      root
>    cpuset: use partition_disable for update_prstate
>    cpuset: remove prs_err clear when notify_partition_change
>
>   kernel/cgroup/cpuset.c | 907 ++++++++++++++++++-----------------------
>   1 file changed, 408 insertions(+), 499 deletions(-)
>