lamina

Some tools for generating and playing with x64 microbenchmarks in user-space, and a kernel module for providing direct access to PMCs. This was written specifically for use on my Ryzen 9 3950X: only Zen 2 machines are supported.

Usage

scripts/config-cpu [enable|disable] is used to toggle options that might affect test results, i.e. SMT and CPU frequency scaling. You're also required to run this when using the kernel module to instrument PMCs because:

• It globally sets CR4.PCE, allowing you to issue RDPMC in user-space without causing an exception
• It disables the NMI watchdog (which consumes the first counter)

You'll also need to build and load the kernel module before using the crate. I'm using this on Linux 5.17 with no [obvious] issues. For example:

$ make
...
$ sudo ./scripts/config-cpu enable
...
$ sudo insmod kernel/lamina.ko
...
$ cargo run --release --bin rdpmc_example