/sys/devices/system/cpu/cpu*/online missing in the latest Jetpack/L4T release

Autonomous Machines Jetson & Embedded Systems Jetson TX1
#1

Hello,

After updating to the L4T R28.2 release, I noticed that the TX1s I had were missing the /sys/devices/system/cpu/cpu*/online and the /sys/devices/system/cpu/cpuquiet/tegra_cpuquiet/enable sysfs devices.

Were they moved to a different location, or is there now a different mechanism to bringing up/down individual CPUs?

Also this means that the instructions on https://elinux.org/Jetson/TX1_Controlling_Performance are now failing. :(

#2

Although I don’t see “tegra_cpuquiet” (R28.2), I do see all of:

/sys/devices/system/cpu/cpu*/online

One detail to consider is that cpu0 is always online, so it won’t have “cpu0/online”.

#3

Good point. cpu1, cpu2 and cpu3 do have the online file. I always checked cpu0 only, it used to have the online file back in R24.x days.

Anyway what about tegra_cpuquiet? We don’t need it anymore?

#4

notthetup,

Yes, tegra_cpuquiet no longer exists on k4.4 TX1, TX2 or AGX Xavier.

The way to enable/disable cpu

To offline (hotunplug) core X
 echo 0 > /sys/devices/system/cpu/cpuX/online
To online (hotplug) core X
 echo 1 > /sys/devices/system/cpu/cpuX/online
To get list of online cores
 cat /sys/devices/system/cpu/online
#5