benchmark: add heap profiler labels overhead benchmarks

Three benchmarks:
- v8/heap-profiler-labels: micro benchmark (1M allocations)
- http/heap-profiler-labels: single-server with ~150KB mixed workload
- http/heap-profiler-realistic: two-server (app + DB) with JSON parse,
  column aggregation, and Buffer allocation per request

Statistical results (20 runs, 1000 rows, Welch t-test):
  none -> sampling:       ~1% overhead
  sampling -> labels:     ~1% overhead
  none -> labels (total): ~2% overhead

Signed-off-by: Rudolf Meijering <skaapgif@gmail.com>

Author: rudolf

benchmark/http/heap-profiler-labels.js

@@ -0,0 +1,88 @@
+'use strict';
+
+// Benchmark: HTTP server throughput impact of heap profiler with labels.
+//
+// Measures requests/sec across three modes:
+// - none: no profiler (baseline)
+// - sampling: profiler active, no labels
+// - sampling-with-labels: profiler active with labels via withHeapProfileLabels
+//
+// Workload per request: ~100KB V8 heap (JSON parse/stringify) + ~50KB Buffer
+// to exercise both HeapProfileLabelsCallback and ProfilingArrayBufferAllocator.
+//
+// Run with compare.js:
+//   node benchmark/compare.js --old ./out/Release/node --new ./out/Release/node \
+//     --runs 10 --filter heap-profiler-labels --set c=50 -- http
+
+const common = require('../common.js');
+const { PORT } = require('../_http-benchmarkers.js');
+const v8 = require('v8');
+
+const bench = common.createBenchmark(main, {
+  mode: ['none', 'sampling', 'sampling-with-labels'],
+  c: [50],
+  duration: 10,
+});
+
+// Build a ~100KB realistic JSON payload template (API response shape).
+const items = [];
+for (let i = 0; i < 200; i++) {
+  items.push({
+    id: i,
+    name: `user-${i}`,
+    email: `user${i}@example.com`,
+    role: 'admin',
+    metadata: { created: '2024-01-01', tags: ['a', 'b', 'c'] },
+  });
+}
+const payloadTemplate = JSON.stringify({ data: items, total: 200 });
+
+function main({ mode, c, duration }) {
+  const http = require('http');
+
+  const interval = 512 * 1024; // 512KB — V8 default, production-realistic.
+
+  if (mode !== 'none') {
+    v8.startSamplingHeapProfiler(interval);
+  }
+
+  const server = http.createServer((req, res) => {
+    const handler = () => {
+      // Realistic mixed workload:
+      // 1. ~100KB V8 heap: JSON parse + stringify (simulates API response building)
+      const parsed = JSON.parse(payloadTemplate);
+      parsed.requestId = Math.random();
+      const body = JSON.stringify(parsed);
+
+      // 2. ~50KB Buffer (simulates response buffering / crypto / compression)
+      const buf = Buffer.alloc(50 * 1024, 0x42);
+
+      // Keep buf reference alive until response is sent.
+      res.writeHead(200, {
+        'Content-Type': 'application/json',
+        'Content-Length': body.length,
+        'X-Buf-Check': buf[0],
+      });
+      res.end(body);
+    };
+
+    if (mode === 'sampling-with-labels') {
+      v8.withHeapProfileLabels({ route: req.url }, handler);
+    } else {
+      handler();
+    }
+  });
+
+  server.listen(PORT, () => {
+    bench.http({
+      path: '/api/bench',
+      connections: c,
+      duration,
+    }, () => {
+      if (mode !== 'none') {
+        v8.stopSamplingHeapProfiler();
+      }
+      server.close();
+    });
+  });
+}

benchmark/http/heap-profiler-realistic.js

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+'use strict';
+
+// Benchmark: realistic app-server + DB-server heap profiler overhead.
+//
+// Architecture: wrk → [App Server :PORT] → [DB Server :PORT+1]
+//
+// The app server fetches JSON rows from the DB server, parses,
+// sums two columns over all rows, and returns the result. This exercises:
+//   - http.get (async I/O + Buffer allocation for response body)
+//   - JSON.parse of realistic DB response (V8 heap allocation)
+//   - Two iteration passes over rows (intermediate values)
+//   - ALS label propagation across async I/O boundary
+//
+// Run with compare.js for statistical significance:
+//   node benchmark/compare.js --old ./out/Release/node --new ./out/Release/node \
+//     --runs 30 --filter heap-profiler-realistic --set rows=1000 -- http
+
+const common = require('../common.js');
+const { PORT } = require('../_http-benchmarkers.js');
+const v8 = require('v8');
+const http = require('http');
+
+const DB_PORT = PORT + 1;
+
+const bench = common.createBenchmark(main, {
+  mode: ['none', 'sampling', 'sampling-with-labels'],
+  rows: [100, 1000],
+  c: [50],
+  duration: 10,
+});
+
+// --- DB Server: pre-built JSON responses keyed by row count ---
+
+function buildDBResponse(n) {
+  const categories = ['electronics', 'clothing', 'food', 'books', 'tools'];
+  const rows = [];
+  for (let i = 0; i < n; i++) {
+    rows.push({
+      id: i,
+      amount: Math.round(Math.random() * 10000) / 100,
+      quantity: Math.floor(Math.random() * 500),
+      name: `user-${String(i).padStart(6, '0')}`,
+      email: `user${i}@example.com`,
+      category: categories[i % categories.length],
+    });
+  }
+  const body = JSON.stringify({ rows, total: n });
+  return { body, len: Buffer.byteLength(body) };
+}
+
+// --- App Server helpers ---
+
+function fetchFromDB(rows) {
+  return new Promise((resolve, reject) => {
+    const req = http.get(
+      `http://127.0.0.1:${DB_PORT}/?rows=${rows}`,
+      (res) => {
+        const chunks = [];
+        res.on('data', (chunk) => chunks.push(chunk));
+        res.on('end', () => {
+          try {
+            resolve(JSON.parse(Buffer.concat(chunks).toString()));
+          } catch (e) {
+            reject(e);
+          }
+        });
+      },
+    );
+    req.on('error', reject);
+  });
+}
+
+function processRows(data) {
+  const { rows } = data;
+  // Two passes — simulates light business logic (column aggregation).
+  let totalAmount = 0;
+  for (let i = 0; i < rows.length; i++) {
+    totalAmount += rows[i].amount;
+  }
+  let totalQuantity = 0;
+  for (let i = 0; i < rows.length; i++) {
+    totalQuantity += rows[i].quantity;
+  }
+  return {
+    totalAmount: Math.round(totalAmount * 100) / 100,
+    totalQuantity,
+    count: rows.length,
+  };
+}
+
+function main({ mode, rows, c, duration }) {
+  // Pre-build DB responses.
+  const dbResponses = {};
+  for (const n of [100, 1000]) {
+    dbResponses[n] = buildDBResponse(n);
+  }
+
+  // Start DB server.
+  const dbServer = http.createServer((req, res) => {
+    const url = new URL(req.url, `http://127.0.0.1:${DB_PORT}`);
+    const n = parseInt(url.searchParams.get('rows') || '1000', 10);
+    const resp = dbResponses[n] || dbResponses[1000];
+    res.writeHead(200, {
+      'Content-Type': 'application/json',
+      'Content-Length': resp.len,
+    });
+    res.end(resp.body);
+  });
+
+  dbServer.listen(DB_PORT, () => {
+    const interval = 512 * 1024;
+    if (mode !== 'none') {
+      v8.startSamplingHeapProfiler(interval);
+    }
+
+    // Start app server.
+    const appServer = http.createServer((req, res) => {
+      const handler = async () => {
+        const data = await fetchFromDB(rows);
+        const result = processRows(data);
+        const body = JSON.stringify(result);
+        res.writeHead(200, {
+          'Content-Type': 'application/json',
+          'Content-Length': Buffer.byteLength(body),
+        });
+        res.end(body);
+      };
+
+      if (mode === 'sampling-with-labels') {
+        v8.withHeapProfileLabels({ route: req.url }, handler);
+      } else {
+        handler();
+      }
+    });
+
+    appServer.listen(PORT, () => {
+      bench.http({
+        path: '/api/data',
+        connections: c,
+        duration,
+      }, () => {
+        if (mode !== 'none') {
+          v8.stopSamplingHeapProfiler();
+        }
+        appServer.close();
+        dbServer.close();
+      });
+    });
+  });
+}

benchmark/v8/heap-profiler-labels.js

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+'use strict';
+
+// Benchmark: overhead of V8 sampling heap profiler with and without labels.
+//
+// Measures per-allocation cost across three modes:
+// - none: no profiler running (baseline)
+// - sampling: profiler active, no labels callback
+// - sampling-with-labels: profiler active with labels via withHeapProfileLabels
+//
+// Run standalone:
+//   node benchmark/v8/heap-profiler-labels.js
+//
+// Run with compare.js for statistical analysis:
+//   node benchmark/compare.js --old ./node-baseline --new ./node-with-labels \
+//     --filter heap-profiler-labels
+
+const common = require('../common.js');
+const v8 = require('v8');
+
+const bench = common.createBenchmark(main, {
+  mode: ['none', 'sampling', 'sampling-with-labels'],
+  n: [1e6],
+});
+
+function main({ mode, n }) {
+  const interval = 512 * 1024; // 512KB — V8 default, production-realistic.
+
+  if (mode === 'sampling') {
+    v8.startSamplingHeapProfiler(interval);
+  } else if (mode === 'sampling-with-labels') {
+    v8.startSamplingHeapProfiler(interval);
+  }
+
+  if (mode === 'sampling-with-labels') {
+    v8.withHeapProfileLabels({ route: '/bench' }, () => {
+      runWorkload(n);
+    });
+  } else {
+    runWorkload(n);
+  }
+
+  if (mode !== 'none') {
+    v8.stopSamplingHeapProfiler();
+  }
+}
+
+function runWorkload(n) {
+  const arr = [];
+  bench.start();
+  for (let i = 0; i < n; i++) {
+    // Allocate objects with string properties — representative of JSON API
+    // workloads. Each object is ~100-200 bytes on the V8 heap.
+    arr.push({ id: i, name: `item-${i}`, value: Math.random() });
+    // Prevent unbounded growth — keep last 1000 to maintain GC pressure
+    // without running out of memory.
+    if (arr.length > 1000) arr.shift();
+  }
+  bench.end(n);
+}