Use spin lock instead of standard lock

[siddontang]

I use crate spin 0.4.6 and find that the spin lock has a better performance than the standard lock.

In our case, we can't hold the lock for a long time, so using spin has a great benefit.

#[bench]
fn bench_lock_write_map(b: &mut Bencher) {
    let m = HashMap::with_capacity(100);
    let l = Arc::new(RwLock::new(m));

    b.iter(||{
        let mut a = l.write().unwrap();
        a.insert(1, 1);
    })
}

#[bench]
fn bench_spinlock_write_map(b: &mut Bencher) {
    let m = HashMap::with_capacity(100);
    let l = Arc::new(spin::RwLock::new(m));

    b.iter(||{
        let mut a = l.write();
        a.insert(1, 1);
    })
}


#[bench]
fn bench_lock_read_map(b: &mut Bencher) {
    let mut m = HashMap::with_capacity(100);
    m.insert(1, 1);
    let l = Arc::new(RwLock::new(m));

    b.iter(||{
        let a = l.read().unwrap();
        a.get(&1).unwrap();
    })
}

#[bench]
fn bench_spinlock_read_map(b: &mut Bencher) {
    let mut m = HashMap::with_capacity(100);
    m.insert(1, 1);
    let l = Arc::new(spin::RwLock::new(m));

    b.iter(||{
        let mut a = l.read();
        a.get(&1).unwrap();
    })
}

test tests::bench_lock_read_map      ... bench:          47 ns/iter (+/- 4)
test tests::bench_lock_write_map     ... bench:          45 ns/iter (+/- 4)
test tests::bench_spinlock_read_map  ... bench:          17 ns/iter (+/- 3)
test tests::bench_spinlock_write_map ... bench:          15 ns/iter (+/- 2)

[overvenus]

Closed via #124