perf-event 0.4.0

perf-event: a Rust interface to Linux performance monitoring

This is a nascent project. Tests and docs are lacking. The design may change.

This uses the Linux perf_event_open API to access performance monitoring hardware and software. Use Builder to create a perf event counter, then use enable and disable to start and stop counting. Call read to get your count.

For example, this counts the number of cycles used by the call to println!. Try adjusting the length of the vector to see the cycle count change.

fn main() -> std::io::Result<()> {
    let mut counter = Builder::new().build()?;

    let vec = (0..=51).collect::<Vec<_>>();

    counter.enable()?;
    println!("{:?}", vec);
    counter.disable()?;

    println!("{} instructions retired", counter.read()?);

    Ok(())
}

At present, Builder measures the PERF_COUNT_HW_INSTRUCTIONS counter. Its description from the perf_event_open(2) man page:

Retired instructions. Be careful, these can be affected by various issues, most notably hardware interrupt counts.

The examples directory includes programs that count other sorts of events.