A quick a dirty test on how long a tokio semaphore takes to add and acquire permits (as a pair)

tokio_semaphore_test.rs

use tokio::sync::Semaphore;
use std::sync::Arc;
use std::time::Instant;

const LOOPS: usize = 1000000;

async fn twiddle(semaphore1: Arc<Semaphore>, semaphore2: Arc<Semaphore>) {
    for _ in 0..LOOPS {
        semaphore1.add_permits(1);

        let permit = semaphore2.acquire().await.unwrap();
        permit.forget();
    }
}

#[tokio::main]
async fn main() {

    let semaphore1 = Arc::new(Semaphore::new(0));
    let semaphore2 = Arc::new(Semaphore::new(0));

    let semaphore1_a = semaphore1.clone();
    let semaphore2_a = semaphore2.clone();

    let start_time = Instant::now();

    let handle1 = tokio::spawn(
        async move {
            twiddle(semaphore1, semaphore2).await;
        }
    );

    let handle2 = tokio::spawn(
        async move {
            twiddle(semaphore2_a, semaphore1_a).await;
        }
    );

    handle1.await.unwrap();
    handle2.await.unwrap();

    dbg!(start_time.elapsed()/(LOOPS as u32));
}