为了比较C和Rust之间的文件I/O性能,我将"test"写入文件100000000次,并从文件100000000次读取4个字节.
与C相比,Rust代码的写入时间是sys的450倍,读取时间是sys的140倍.
我怀疑有更好的方法来实现快速I/O;如何提高Rust中文件I/O的性能?
$ rustc --version
rustc 1.16.0
$ rustc rswrite.rs -C opt-level=3 # Rust for writing
$ time ./rswrite
real 1m8.411s
user 0m3.817s
sys 1m4.533s
$ rustc rsread.rs -C opt-level=3 # Rust for reading
$ time ./rsread
real 0m18.077s
user 0m2.130s
sys 0m15.910s
$ gcc -O3 cwrite.c -ocwrite # C for writing
$ time ./cwrite
real 0m1.564s
user 0m1.397s
sys 0m0.143s
$ gcc -O3 cread.c -ocread # C for reading
$ time ./cread
real 0m1.353s
user 0m1.240s
sys 0m0.113s
书写代码:
use std::fs;
use std::io::Write;
fn main() {
let b = b"test";
let mut f = fs::File::create("rs.dump").unwrap();
for _ in 0 .. 100_000_000 {
f.write(b).unwrap();
}
}
用于阅读的防 rust 代码:
use std::{fs, mem};
use std::io::Read;
fn main() {
let mut f = fs::File::open("rs.dump").unwrap();
let mut b: [u8; 4] = unsafe { mem::uninitialized() };
for _ in 0 .. 100_000_000 {
f.read_exact(&mut b).unwrap();
}
}
C编写代码:
#include <stdio.h>
#define N 100000000
int main()
{
const char *teststr = "test";
FILE *fp = fopen("c.dump", "wb");
unsigned long long i;
for (i=0; i<N; i++) fwrite(teststr, 4, 1, fp);
fclose(fp);
return 0;
}
C阅读代码:
#include <stdio.h>
#define N 100000000
int main() {
FILE *fp = fopen("c.dump", "rb");
long long i;
char buf[4];
for (i=0; i<N; i++) fread(buf, 4, 1, fp);
fclose(fp);
return 0;
}