linux-kernel - [PATCH RFC v2 00/22] cpuset: rework local partition logic

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Message-Id: <20251025064844.495525-1-chenridong@huaweicloud.com>
Date: Sat, 25 Oct 2025 06:48:22 +0000
From: Chen Ridong <chenridong@...weicloud.com>
To: longman@...hat.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: [PATCH RFC v2 00/22] cpuset: rework local partition logic

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. Fix a bug that isolcpus stat in root partition.

2. Infrastructure Preparation (Patches 2-3):
   - Code cleanup and preparation for the refactoring work

3. Introduce partition operation helpers (Patches 4-6):
   - Intoduce out partition_enable(), partition_disable(), and
     partition_update() functions.

4. Use new helpers for remote partition (Patches 7-9)

5. Local Partition Implementation (Patches 10-13):
   - Separate update_parent_effective_cpumask() into dedicated functions:
     * local_partition_enable()
     * local_partition_disable()
     * local_partition_invalidate()
     * local_partition_update()

6. Optimization and Cleanup (Patches 14-22):
   - Remove redundant partition-related operations
   - Additional optimizations based on the new architecture

---

Changes in v2:
- Added bugfix for root partition isolcpus at series start.
- Completed helper function implementations when first introduced.
- Split larger patches into smaller, more reviewable units.
- Incorporated feedback from Longman.

Chen Ridong (22):
  cpuset: fix isolcpus stay in root when isolated partition changes to
    root
  cpuset: add early empty cpumask check in partition_xcpus_add/del
  cpuset: generalize validate_partition() interface
  cpuset: introduce partition_enable()
  cpuset: introduce partition_disable()
  cpuset: introduce partition_update()
  cpuset: use partition_enable() for remote partition enablement
  cpuset: use partition_disable() for remote partition disablement
  cpuset: use partition_update() for remote partition update
  cpuset: introduce local_partition_enable()
  cpuset: introduce local_partition_disable()
  cpuset: introduce local_partition_invalidate()
  cpuset: introduce local_partition_update()
  cpuset: remove update_parent_effective_cpumask
  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: use validate_local_partition in local_partition_enable
  cpuset: introduce validate_remote_partition
  cpuset: simplify update_prstate() function
  cpuset: remove prs_err clear when notify_partition_change

 kernel/cgroup/cpuset.c | 1000 +++++++++++++++++++---------------------
 1 file changed, 463 insertions(+), 537 deletions(-)

-- 
2.34.1