Comparing atomic and non-atomic additions in Rust.

atomics.rs

// This should be "benches/atomics.rs", but gists can't have subdirectories.

use std::sync::atomic::{AtomicUsize, Ordering};

use criterion::{Criterion, Fun, criterion_group, criterion_main};

fn add1(n: usize) -> usize {
    n + 1
}

fn add1_atomic(n: AtomicUsize) -> AtomicUsize {
    n.fetch_add(1, Ordering::Relaxed);
    n
}

fn benchmark_add(c: &mut Criterion) {
    let add = Fun::new("Non atomic", |b, i| b.iter(|| add1(*i)));
    let atomic_add = Fun::new("atomic", |b, i| b.iter(|| add1_atomic(AtomicUsize::new(*i))));

    c.bench_functions("Add", vec![add, atomic_add], 0);
}

criterion_group!(benches, benchmark_add);
criterion_main!(benches);

Cargo.toml

[package]
name = "tmp"
version = "0.1.0"
authors = ["Thomas de Zeeuw <[email protected]>"]
edition = "2018"

[dev-dependencies]
criterion = "0.2"

[[bench]]
name = "atomics"
harness = false

results

Add/Non atomic          time:   [336.94 ps 338.56 ps 340.38 ps]
Found 18 outliers among 100 measurements (18.00%)
  4 (4.00%) high mild
  14 (14.00%) high severe
Add/atomic              time:   [11.412 ns 11.465 ns 11.523 ns]
Found 13 outliers among 100 measurements (13.00%)
  6 (6.00%) high mild
  7 (7.00%) high severe