benchmark: add pm startup benchmark

PR-URL: nodejs#48905
Reviewed-By: Paolo Insogna <paolo@cowtech.it>
Reviewed-By: Rich Trott <rtrott@gmail.com>

benchmark/permission/permission-startup.js

@@ -0,0 +1,59 @@
+'use strict';
+
+const common = require('../common.js');
+const path = require('path');
+const { spawnSync } = require('child_process');
+
+function mockFiles(n, prefix = '/tmp') {
+  const files = [];
+  for (let i = 0; i < n; ++i) {
+    files.push(prefix + '/file' + i + '.js');
+  }
+
+  return files;
+}
+
+const bench = common.createBenchmark(main, {
+  script: [
+    'test/fixtures/semicolon',
+  ],
+  prefixPath: ['/tmp'],
+  nFiles: [10, 100, 1000],
+  count: [30],
+});
+
+function spawnProcess(script, bench, state) {
+  const cmd = process.execPath || process.argv[0];
+  while (state.finished < state.count) {
+    const child = spawnSync(cmd, script);
+    if (child.status !== 0) {
+      console.log('---- STDOUT ----');
+      console.log(child.stdout.toString());
+      console.log('---- STDERR ----');
+      console.log(child.stderr.toString());
+      throw new Error(`Child process stopped with exit code ${child.status}`);
+    }
+    state.finished++;
+    if (state.finished === 0) {
+      // Finished warmup.
+      bench.start();
+    }
+
+    if (state.finished === state.count) {
+      bench.end(state.count);
+    }
+  }
+}
+
+function main({ count, script, nFiles, prefixPath }) {
+  script = path.resolve(__dirname, '../../', `${script}.js`);
+  const files = mockFiles(nFiles, prefixPath).join(',');
+  const optionsWithScript = [
+    '--experimental-permission',
+    `--allow-fs-read=${files},${script}`,
+    script,
+  ];
+  const warmup = 3;
+  const state = { count, finished: -warmup };
+  spawnProcess(optionsWithScript, bench, state);
+}