linux-kernel - [PATCH v2 0/1] tick/nohz: Expose housekeeping CPUs in sysfs

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Message-ID: <20251007012958.16666-1-atomlin@atomlin.com>
Date: Mon,  6 Oct 2025 21:29:57 -0400
From: Aaron Tomlin <atomlin@...mlin.com>
To: gregkh@...uxfoundation.org,
	rafael@...nel.org,
	dakr@...nel.org
Cc: riel@...riel.com,
	frederic@...nel.org,
	atomlin@...mlin.com,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 0/1] tick/nohz: Expose housekeeping CPUs in sysfs

Expose the current system-defined list of housekeeping CPUs in a new
sysfs file: /sys/devices/system/cpu/housekeeping.

This provides userspace performance tuning tools and resource managers
with a canonical, reliable method to accurately identify the cores
responsible for essential kernel maintenance workloads (RCU, timer
callbacks, and unbound workqueues). Currently, tooling must manually
calculate the housekeeping set by parsing complex kernel boot parameters
(like isolcpus= and nohz_full=) and system topology, which is prone to
error. This dedicated file simplifies the configuration of low-latency
workloads.

Changes since v1 [1]:

 - Refactor to use an if statement (Greg KH)
 - Use DEVICE_ATTR_RO() instead (Greg KH)
 - Document the new file under Documentation/ABI (Greg KH)

[1]: https://lore.kernel.org/lkml/20251006005853.76335-1-atomlin@atomlin.com/

Aaron Tomlin (1):
  tick/nohz: Expose housekeeping CPUs in sysfs

 .../ABI/testing/sysfs-devices-system-cpu          | 11 +++++++++++
 drivers/base/cpu.c                                | 15 +++++++++++++++
 2 files changed, 26 insertions(+)

-- 
2.49.0