Create fixed sized vector

performane_test.rs

#![feature(test)]
extern crate test;
use test::Bencher;

fn first(buffer_size: usize) -> Vec<u8> {
    vec![0; buffer_size]
}

fn second(buffer_size: usize) -> Vec<u8> {
    std::iter::repeat(0u8).take(buffer_size).collect()
}

#[bench]
fn first_bench(b: &mut Bencher) {
    b.iter(|| first(100));
}

#[bench]
fn second_bench(b: &mut Bencher) {
    b.iter(|| second(100));
}

result

$ cargo bench

running 2 tests
test first_bench  ... bench:          22 ns/iter (+/- 0)
test second_bench ... bench:          34 ns/iter (+/- 1)