perf_hooks: improve http2 import

[fanatid]

Checklist

• make -j4 test (UNIX) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

Nearly ~119ns for each collectHttp2Stats call.

const http2 = internalBinding('http2'); => 20001: 36.200362ms
if (http2 === undefined) http2 = internalBinding('http2'); => 20001: 33.814263ms
(36.200362 - 33.814263) * 1e6 / 20001 = 119

Same lazy require in net module: https://github.com/nodejs/node/blob/v12.9.1/lib/net.js#L940

Benchmarked with:

const http2 = require('http2')
const perf_hooks = require('perf_hooks')

let firstImport = true
let sum = 0
let cnt = 0
process.once('beforeExit', () => console.log(`${cnt}: ${sum.toFixed(6)}ms`))

const obs = new perf_hooks.PerformanceObserver((items) => {
  const entry = items.getEntries()[0]
  if (entry.entryType !== 'measure') return

  if (firstImport) {
    firstImport = false
    return
  }

  sum += entry.duration
  cnt += 1
})
obs.observe({ entryTypes: ['measure', 'http2'] })

const server = http2.createServer({}, (req, res) => res.end('ok')).listen(8000)
server.once('listening', async () => {
  const client = http2.connect('http://localhost:8000')
  await Promise.all(new Array(1e4).fill(null).map(() => {
    return new Promise((resolve) => client.request().on('data', () => {}).once('close', resolve).end())
  }))

  client.close()
  server.close()
})

Code in perf_hooks.js was changed to:

  performance.mark('collectHttp2StatsImportStart');
  // const http2 = internalBinding('http2');
  if (http2 === undefined) http2 = internalBinding('http2');
  performance.mark('collectHttp2StatsImportEnd');
  performance.measure('collectHttp2Stats', 'collectHttp2StatsImportStart', 'collectHttp2StatsImportEnd');

[trivikr]

CI: https://ci.nodejs.org/job/node-test-pull-request/25337/

[nodejs-github-bot]

CI: https://ci.nodejs.org/job/node-test-pull-request/25337/

[Trott]

Landed in 6186302