I have an ARM64 Cortex-A72 board running Linux 5.4.47. I want to check if the CPU hot-plugging is working correctly (it's needed for one project I want to use).
Kernel has
CONFIG_HOTPLUG_CPU enabled, but I don't have
/sys/devices/system/cpu/cpuX/online for any CPU -
and I don't know how I could turn off a CPU.
Code:
/sys/devices/system/cpu]# ls -l
total 0
-r--r--r-- 1 root root 4.0K Jan 1 00:00 consumers
drwxr-xr-x 7 root root 0 Jan 1 00:00 cpu0
drwxr-xr-x 7 root root 0 Jan 1 00:00 cpu1
drwxr-xr-x 7 root root 0 Jan 1 00:00 cpu2
drwxr-xr-x 7 root root 0 Jan 1 00:00 cpu3
drwxr-xr-x 2 root root 0 Jan 1 00:00 cpuidle
drwxr-xr-x 2 root root 0 Jan 1 00:00 hotplug
-r--r--r-- 1 root root 4.0K Jan 1 00:00 isolated
-r--r--r-- 1 root root 4.0K Jan 1 00:00 kernel_max
-r--r--r-- 1 root root 4.0K Jan 1 00:00 modalias
-r--r--r-- 1 root root 4.0K Jan 1 00:00 nohz_full
-r--r--r-- 1 root root 4.0K Jan 1 00:13 offline
-r--r--r-- 1 root root 4.0K Jan 1 00:00 online
-r--r--r-- 1 root root 4.0K Jan 1 00:00 possible
drwxr-xr-x 2 root root 0 Jan 1 00:00 power
-r--r--r-- 1 root root 4.0K Jan 1 00:00 present
drwxr-xr-x 2 root root 0 Jan 1 00:00 smt
-r--r--r-- 1 root root 4.0K Jan 1 00:00 suppliers
-rw-r--r-- 1 root root 4.0K Jan 1 00:00 uevent
drwxr-xr-x 2 root root 0 Jan 1 00:00 vulnerabilities
Code:
/sys/devices/system/cpu/cpu2]# ls -l
total 0
drwxr-xr-x 5 root root 0 Jan 1 00:07 cache
-r--r--r-- 1 root root 4.0K Jan 1 00:06 consumers
-r--r--r-- 1 root root 4.0K Jan 1 00:06 cpu_capacity
-r-------- 1 root root 4.0K Jan 1 00:06 crash_notes
-r-------- 1 root root 4.0K Jan 1 00:06 crash_notes_size
drwxr-xr-x 2 root root 0 Jan 1 00:06 hotplug
lrwxrwxrwx 1 root root 0 Jan 1 00:06 node0 -> ../../node/node0
lrwxrwxrwx 1 root root 0 Jan 1 00:06 of_node -> ../../../../firmware/devicetree/base/cpus/cpu@2
drwxr-xr-x 2 root root 0 Jan 1 00:06 power
drwxr-xr-x 3 root root 0 Jan 1 00:12 regs
lrwxrwxrwx 1 root root 0 Jan 1 00:06 subsystem -> ../../../../bus/cpu
-r--r--r-- 1 root root 4.0K Jan 1 00:06 suppliers
drwxr-xr-x 2 root root 0 Jan 1 00:03 topology
-rw-r--r-- 1 root root 4.0K Jan 1 00:06 uevent
The
hotplug contains files
target,
state and
fail. The power contains
runtime_active_time,
pm_qos_resume_latency_us,
runtime_status,
autosuspend_delay_ms,
runtime_suspended_time and
control.
