linux-kernel - [PATCH -next 00/21] cpuset: rework local partition logic

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Message-Id: <20251117024627.1128037-1-chenridong@huaweicloud.com>
Date: Mon, 17 Nov 2025 02:46:06 +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 -next 00/21] 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. Infrastructure Preparation (Patches 1-2):
   - Code cleanup and preparation for the refactoring work

2. Introduce partition operation helpers (Patches 3-5):
   - Introduce out partition_enable(), partition_disable(), and
     partition_update() functions.

3. Use new helpers for remote partition (Patches 6-8)

4. Local Partition Implementation (Patches 9-12):
   - Separate update_parent_effective_cpumask() into dedicated functions:
     * local_partition_enable()
     * local_partition_disable()
     * local_partition_update()

5. Optimization and Cleanup (Patches 13-21):
   - Remove redundant partition-related operations
   - Additional optimizations based on the new architecture

base-commit: 6d7e7251d03f98f26f2ee0dfd21bb0a0480a2178

---

Changes from RFC v2:
1. Dropped the bugfix (already merged/fixed upstream)
2. Rebased onto next
3. Introduced partition_switch to handle root state switches
4. Directly use local_partition_disable()—no longer first introduce
   local_partition_invalidate() before unifying the two
5. Incorporated modifications based on Longman's suggestions

Changes in RFC v1:
1. Added bugfix for root partition isolcpus at series start.
2. Completed helper function implementations when first introduced.
3. Split larger patches into smaller, more reviewable units.
4. Incorporated feedback from Longman.

Chen Ridong (21):
  cpuset: add early empty cpumask check in partition_xcpus_add/del
  cpuset: generalize the 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: user local_partition_disable() to invalidate local partition
  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: use partition_disable for compute_partition_effective_cpumask
  cpuset: use validate_local_partition in local_partition_enable
  cpuset: introduce validate_remote_partition
  cpuset: simplify the update_prstate() function
  cpuset: remove prs_err clear when notify_partition_change
  cpuset: Remove unnecessary validation in partition_cpus_change

 kernel/cgroup/cpuset.c | 1014 ++++++++++++++++++----------------------
 1 file changed, 453 insertions(+), 561 deletions(-)

-- 
2.34.1