源码快照 @ 2026-09-01 (source-only, 剔除非源码素材)

scripts/perf/session-switch-commits.mjs

@@ -0,0 +1,96 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+/**
+ * How many React commits one session switch costs, and how much of each is a
+ * full-tree render (#4109).
+ *
+ * Usage, against a running dev app with `--remote-debugging-port=9334`:
+ *
+ *   node scripts/perf/session-switch-commits.mjs <label> [port]
+ *
+ * Reloads the page to install `react-commit-probe.js` before React boots, then
+ * switches sessions several times and reports the median. Read the medians, not
+ * a single row: the first switch after a reload pays for caches the rest do
+ * not, which is why row 1 is a warm-up and is excluded.
+ *
+ * NEVER compare two numbers from two app launches. Restarting the app moves
+ * these metrics by an order of magnitude while the spread inside one instance
+ * is small; an A/B has to alternate configurations inside one running instance
+ * and compare paired trials.
+ */
+
+import { readFileSync, writeFileSync } from 'node:fs';
+import { join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+import { clickSessionRow, connectRenderer, median, sleep, DEFAULT_PORT } from './cdp-client.mjs';
+
+const here = fileURLToPath(new URL('.', import.meta.url));
+const label = process.argv[2] ?? 'run';
+const port = Number(process.argv[3] ?? DEFAULT_PORT);
+
+/** A full-tree render: React re-rendered essentially everything under the root. */
+const FULL_TREE_FIBERS = 1000;
+const SETTLE_MS = 2500;
+const BOOT_MS = 9000;
+const ROWS = [2, 3, 4, 5, 6, 7, 8, 9];
+
+const client = await connectRenderer(port);
+await client.ready;
+await client.send('Page.enable');
+await client.send('Page.addScriptToEvaluateOnNewDocument', {
+  source: readFileSync(join(here, 'react-commit-probe.js'), 'utf8'),
+});
+await client.send('Page.reload');
+await sleep(BOOT_MS);
+
+await clickSessionRow(client, 1);
+await sleep(3000);
+
+const results = [];
+for (const row of ROWS) {
+  await client.evaluate(
+    '__MAKA_PROBE__.commits.length = 0; __MAKA_PROBE__.dispatches.length = 0; __MAKA_PROBE__.arm = true',
+  );
+  await clickSessionRow(client, row);
+  await sleep(SETTLE_MS);
+  await client.evaluate('__MAKA_PROBE__.arm = false');
+  const { commits } = JSON.parse(
+    await client.evaluate('JSON.stringify({ commits: __MAKA_PROBE__.commits })'),
+  );
+  const fullTree = commits.filter((commit) => commit.total > FULL_TREE_FIBERS);
+  const renderRoots = {};
+  for (const commit of fullTree) {
+    const name = commit.rr[0]?.name ?? '?';
+    renderRoots[name] = (renderRoots[name] ?? 0) + 1;
+  }
+  const rendered = commits.reduce((sum, commit) => sum + commit.total, 0);
+  results.push({ row, commits: commits.length, fullTree: fullTree.length, renderRoots, rendered });
+  console.log(
+    `row ${row}: commits=${commits.length} fullTree=${fullTree.length} renderedFibers=${rendered} roots=${JSON.stringify(renderRoots)}`,
+  );
+}
+
+console.log(
+  `\n[${label}] median commits=${median(results.map((r) => r.commits))} ` +
+    `fullTree=${median(results.map((r) => r.fullTree))} ` +
+    `renderedFibers=${median(results.map((r) => r.rendered))}`,
+);
+writeFileSync(`session-switch-commits-${label}.json`, `${JSON.stringify(results, null, 1)}\n`);
+client.close();