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

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Message-Id: <20250928071306.3797436-1-chenridong@huaweicloud.com>
Date: Sun, 28 Sep 2025 07:12:50 +0000
From: Chen Ridong <chenridong@...weicloud.com>
To: longman@...hat.com,
	tj@...nel.org,
	hannes@...xchg.org,
	mkoutny@...e.com
Cc: cgups@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	lujialin4@...wei.com,
	chenridong@...wei.com
Subject: [PATCH -next RFC 00/16] 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. 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

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(-)

-- 
2.34.1