[NodeJs] Overhead of Promise(async/await) (more serious than you think!)

Just see following test.

Environment

• OS: 4.15.0-47-generic #50-Ubuntu SMP.
• CPU: Intel(R) Xeon(R) CPU E5-2697 v3 @ 2.60GHz
• NodeJs: 10.15.3

Normal

function f() {}

async function main() {
    let tm = -Date.now();
    for (let i = 0; i < 100000; i++) {
        f();
    }
    tm += Date.now();
    console.log(tm);
}
main()

$ node test.js
3

With operations

function f() {
    a = [];
    for (let i = 0; i < 30; i++) { a.push(i); }
}

async function main() {
    let tm = -Date.now();
    for (let i = 0; i < 100000; i++) {
        f();
    }
    tm += Date.now();
    console.log(tm);
}
main()

$ node test.js
27

With await

function f() {}

async function main() {
    let tm = -Date.now();
    for (let i = 0; i < 100000; i++) {
        await f();
    }
    tm += Date.now();
    console.log(tm);
}
main()

$ node test.js
19

With async/await

async function f() {}

async function main() {
    let tm = -Date.now();
    for (let i = 0; i < 100000; i++) {
        await f();
    }
    tm += Date.now();
    console.log(tm);
}
main()

$ node test.js
26