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User-mode access to ARMv8 PMU cycle counters

See https://github.com/thoughtpolice/enable_arm_pmu for details.

This repository contains a kernel module and library.

ARMv8 performance monitor units (PMUs) are only available on ARMv8 machines. In general, this means you'll need a Cortex-A53 or better (A57, X-Gene 1, etc.)

Beware that the registers set by this module can be reset by the kernel, such as when a core goes to sleep. For instance, on a NVidia Jetson TX1, one need to disable idle modes by running as root:

for X in $(seq 0 3); do for Y in $(seq 1 6); do echo 1 > /sys/devices/system/cpu/cpu$X/cpuidle/state$Y/disable ; done ; done

Testing

To compile, load, test and remove the module, you can just run:

$ sudo make runtests

Tested on

  • Applied Micro X-C1 Fedora 21
  • NVidia Jetson TX1 L4T 28.1 (based on Ubuntu)
  • Odroid-C2 Ubuntu 18.04.02