08-性能优化与安全权衡

criterion + flamegraph

****Vec > LinkedList CPU 64B#[repr(C)]

---

• Vec::with_capacity(n) realloc
• String::with_capacity(n)
• smallvec / tinyvec
• bytes crate buffer

****#[inline] / #[inline(always)] Profile-Guided OptimizationPGOBOLT

**** get_unchecked()unsafeunsafe invariant

:

---

//  realloc
let mut v = Vec::with_capacity(1000);
for i in 0..1000 { v.push(i); }
 
// 
use std::borrow::Cow;
fn process(s: Cow<str>) -> Cow<str> {
 if s.len() > 100 { Cow::Owned(s[..100].to_string()) }
 else { s }
}
 
// 
#[inline]
fn hot_path(x: i32) -> i32 { x * 2 }
 
// criterion 
use criterion::{criterion_group, criterion_main, Criterion};
fn bench_add(c: &mut Criterion) {
 c.bench_function("add", |b| b.iter(|| add(2, 3)));
}
criterion_group!(benches, bench_add);
criterion_main!(benches);

cargo bench
cargo flamegraph	CPU
cargo bloat
perf record	Linux
heaptrack
cachegrind

---