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

scripts/perf/session-switch-busy-js.mjs

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+/*
+ * 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.
+ */
+
+/**
+ * Renderer busy JS per session switch, with the top self-time entries (#4109).
+ *
+ * Usage, against a running dev app with `--remote-debugging-port=9334`:
+ *
+ *   node scripts/perf/session-switch-busy-js.mjs [port] [trials]
+ *
+ * This reports one configuration: whatever the running build does. A before/
+ * after needs both configurations reachable from ONE running instance — see the
+ * README for how to get that from a throwaway worktree instead of from a switch
+ * carried in product code.
+ *
+ * Sampling at 100µs. Busy time is every sample that is not `(idle)` or
+ * `(program)`; the top-8 self-time list is there to show WHERE the time is, and
+ * on this workload it is deliberately flat — about a thousand cheap fibers, no
+ * hot component. A change that only moves the top entry around has not moved
+ * the total.
+ *
+ * The same discipline as the commit counter: alternate configurations inside
+ * ONE running instance and compare paired trials. Numbers from two launches are
+ * not comparable.
+ */
+
+import { clickSessionRow, connectRenderer, median, sleep, DEFAULT_PORT } from './cdp-client.mjs';
+
+const positional = process.argv.slice(2).filter((arg) => !arg.startsWith('--'));
+const port = Number(positional[0] ?? DEFAULT_PORT);
+const trials = Number(positional[1] ?? 5);
+const SETTLE_MS = 2000;
+
+const client = await connectRenderer(port);
+await client.ready;
+await client.send('Profiler.enable');
+
+// The commit probe walks the fiber tree on every commit. Left armed it lands in
+// the profile as the app's own work.
+await client.evaluate('globalThis.__MAKA_PROBE__ && (__MAKA_PROBE__.arm = false)').catch(() => {});
+
+async function measureSwitch(row) {
+  await client.send('Profiler.setSamplingInterval', { interval: 100 });
+  await client.send('Profiler.start');
+  await clickSessionRow(client, row);
+  await sleep(SETTLE_MS);
+  const { profile } = await client.send('Profiler.stop');
+
+  const byId = new Map(profile.nodes.map((node) => [node.id, node]));
+  const selfTime = new Map();
+  const deltas = profile.timeDeltas ?? [];
+  let busy = 0;
+  let idle = 0;
+  for (let i = 0; i < profile.samples.length; i++) {
+    const node = byId.get(profile.samples[i]);
+    const dt = (deltas[i] ?? 0) / 1000;
+    const name = node?.callFrame?.functionName || '(anonymous)';
+    if (name === '(idle)' || name === '(program)') {
+      idle += dt;
+      continue;
+    }
+    busy += dt;
+    const file = (node?.callFrame?.url || '').split('/').pop() || '';
+    const key = `${name} @${file}:${node?.callFrame?.lineNumber}`;
+    selfTime.set(key, (selfTime.get(key) ?? 0) + dt);
+  }
+  return { busy, idle, selfTime };
+}
+
+function printTop(selfTime) {
+  for (const [key, value] of [...selfTime.entries()].sort((a, b) => b[1] - a[1]).slice(0, 8)) {
+    console.log(`    ${value.toFixed(0)}ms  ${key.slice(0, 110)}`);
+  }
+}
+
+const busyPerSwitch = [];
+for (let trial = 0; trial < trials; trial++) {
+  const row = 2 + trial;
+  const { busy, idle, selfTime } = await measureSwitch(row);
+  busyPerSwitch.push(busy);
+  console.log(`row ${row}: busyJS=${busy.toFixed(0)}ms idle=${idle.toFixed(0)}ms`);
+  printTop(selfTime);
+}
+console.log(`\nmedian busy JS per switch = ${median(busyPerSwitch).toFixed(0)}ms`);
+
+client.close();