benchmark: add chunked-encoding benchmark

benchmark/http/chunked.js

@@ -0,0 +1,42 @@
+// When calling .end(buffer) right away, this triggers a "hot path"
+// optimization in http.js, to avoid an extra write call.
+//
+// However, the overhead of copying a large buffer is higher than
+// the overhead of an extra write() call, so the hot path was not
+// always as hot as it could be.
+//
+// Verify that our assumptions are valid.
+
+var common = require('../common.js');
+var PORT = common.PORT;
+
+var bench = common.createBenchmark(main, {
+  num: [1, 4, 8, 16],
+  size: [1, 64, 256],
+  c: [100]
+});
+
+function main(conf) {
+  http = require('http');
+  var chunk = new Buffer(conf.size);
+  chunk.fill('8');
+
+  var args = ['-r', 5000, '-t', 8, '-c', conf.c];
+
+  var server = http.createServer(function(req, res) {
+    function send(left) {
+      if (left === 0) return res.end();
+      res.write(chunk);
+      setTimeout(function() {
+        send(left - 1);
+      }, 0);
+    }
+    send(conf.num);
+  });
+
+  server.listen(common.PORT, function() {
+    bench.http('/', args, function() {
+      server.close();
+    });
+  });
+}