From cd22926af45400093738c758b6749de8035ed5a8 Mon Sep 17 00:00:00 2001 From: Aaron Tomlin Date: Fri, 10 Oct 2025 21:28:53 -0400 Subject: 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. Signed-off-by: Aaron Tomlin Link: https://patch.msgid.link/20251011012853.7539-2-atomlin@atomlin.com Signed-off-by: Greg Kroah-Hartman --- Documentation/ABI/testing/sysfs-devices-system-cpu | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'Documentation/ABI/testing/sysfs-devices-system-cpu') diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu index 8aed6d94c4cd..3a05604c21bf 100644 --- a/Documentation/ABI/testing/sysfs-devices-system-cpu +++ b/Documentation/ABI/testing/sysfs-devices-system-cpu @@ -764,6 +764,17 @@ Description: participate in load balancing. These CPUs are set by boot parameter "isolcpus=". +What: /sys/devices/system/cpu/housekeeping +Date: Oct 2025 +Contact: Linux kernel mailing list +Description: + (RO) the list of logical CPUs that are designated by the kernel as + "housekeeping". Each CPU are responsible for handling essential + system-wide background tasks, including RCU callbacks, delayed + timer callbacks, and unbound workqueues, minimizing scheduling + jitter on low-latency, isolated CPUs. These CPUs are set when boot + parameter "isolcpus=nohz" or "nohz_full=" is specified. + What: /sys/devices/system/cpu/crash_hotplug Date: Aug 2023 Contact: Linux kernel mailing list -- cgit v1.2.3