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February 12, 2026 13:09
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bench between CAS operations' weak and strong versions in rust
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| use criterion::{black_box, criterion_group, criterion_main, Criterion}; | |
| use std::sync::atomic::{AtomicUsize, Ordering}; | |
| /// 显式地使用 compare_exchange_weak 来模拟 compare_exchange (strong) 的语义 | |
| /// 只有当值真的不相等时才返回 Err，虚假失败会在内部循环掉 | |
| fn compare_exchange_weak_wrapped( | |
| atomic: &AtomicUsize, | |
| current: usize, | |
| new: usize, | |
| ) -> Result<usize, usize> { | |
| loop { | |
| match atomic.compare_exchange_weak(current, new, Ordering::SeqCst, Ordering::Relaxed) { | |
| // 情况 1: 成功了，直接返回 | |
| Ok(v) => return Ok(v), | |
| // 情况 2: 失败了，检查是“真失败”还是“虚假失败” | |
| Err(actual) => { | |
| if actual != current { | |
| // 真失败：值确实被别人改了 | |
| return Err(actual); | |
| } | |
| // 虚假失败：值没变，继续循环重试 | |
| continue; | |
| } | |
| } | |
| } | |
| } | |
| fn bench_cas_semantics(c: &mut Criterion) { | |
| let mut group = c.benchmark_group("Atomic_CAS_Semantics"); | |
| let initial_val = 0; | |
| // 1. 标准 Strong 语义 (由标准库/硬件提供) | |
| group.bench_function("strong_native", |b| { | |
| let atomic = AtomicUsize::new(initial_val); | |
| b.iter(|| { | |
| let current = black_box(initial_val); | |
| let new = black_box(initial_val + 1); | |
| // 每次成功后重置，确保测试的是单次冲突/成功情况 | |
| let _ = atomic.compare_exchange(current, new, Ordering::SeqCst, Ordering::Relaxed); | |
| atomic.store(initial_val, Ordering::Relaxed); | |
| }) | |
| }); | |
| // 2. 用 Weak 封装出的 Strong 语义 (手动套循环) | |
| group.bench_function("weak_wrapped", |b| { | |
| let atomic = AtomicUsize::new(initial_val); | |
| b.iter(|| { | |
| let current = black_box(initial_val); | |
| let new = black_box(initial_val + 1); | |
| // 调用我们自己封装的函数 | |
| let _ = compare_exchange_weak_wrapped(&atomic, current, new); | |
| atomic.store(initial_val, Ordering::Relaxed); | |
| }) | |
| }); | |
| group.finish(); | |
| } | |
| criterion_group!(benches, bench_cas_semantics); | |
| criterion_main!(benches); |
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