question. How setImmediate improve performance?

[ChangJoo-Park]

Hello @pi0 . I can not find for place to question. So I leave my question here.

I saw yesterday your commit. I understood early return (break to return) is nice pattern in the upper diff src/app.ts.
but, I didn't understand to use setImmediate. All of request already asynchronous. Why need Promise with setImmediate ?

I tried to benchmark before / after setImmediate . I got almost same result.

[pi0]

Hi @ChangJoo-Park. Nice that you checked :) To be honest I've not clear idea why. But you can try yarn profile script to see flame-graph (yarn build is required on a change). It seems event loop gets blocked for sending response without setImmediate. And BTW I've inspired deferring send from connect.

I tried to benchmark before / after setImmediate . I got almost same result.

What is you node version and testing method? For me it was order of 15 percent in node 14

[ChangJoo-Park]

Thank you for reply! I retry with yarn profile Please see result below.
I use Node.js 14 on WSL. 0x cannot launch browser with 0x 😭 I'll fix script and rerun for my env.

I tried to benchmark before / after setImmediate . I got almost same result.

Before I try I saw only throughput. It slightly same.

weird result express with setImmediate

h3's the way of return response is just return something, It is not same with express.

So. I try express with this code. always 'just res.send' faster than with setImmediate.

app.get('/', (req, res) => {
  return res.send({ hello: 'world' })
})

app.get('/', (req, res) => {
  setImmediate(() => res.send({ hello: 'world' }))
})

[ChangJoo-Park]

h3 use promise with setImmediate for nitro at this time. I understood this issue.