streams: 5% throughput gain when sending small chunks

Improves the performance when moving small buffers by 5%,
and it adds a benchmark to avoid regression in that area.
In all other cases it is equally performant to current master.

Full performance results available at:
https://gist.github.com/mcollina/717c35ad07d15710b6b9.

PR-URL: https://github.com/nodejs/node/pull/4354
Reviewed-By: James M Snell <jasnell@gmail.com>

1 files changed, 96 insertions, 0 deletions

diff --git a/benchmark/net/net-c2s-cork.js b/benchmark/net/net-c2s-cork.js
new file mode 100644
index 0000000000..5f8e0fa435
--- /dev/null
+++ b/benchmark/net/net-c2s-cork.js
@@ -0,0 +1,96 @@
+// test the speed of .pipe() with sockets
+
+var common = require('../common.js');
+var PORT = common.PORT;
+
+var bench = common.createBenchmark(main, {
+  len: [4, 8, 16, 32, 64, 128, 512, 1024],
+  type: ['buf'],
+  dur: [5],
+});
+
+var dur;
+var len;
+var type;
+var chunk;
+var encoding;
+
+function main(conf) {
+  dur = +conf.dur;
+  len = +conf.len;
+  type = conf.type;
+
+  switch (type) {
+    case 'buf':
+      chunk = new Buffer(len);
+      chunk.fill('x');
+      break;
+    case 'utf':
+      encoding = 'utf8';
+      chunk = new Array(len / 2 + 1).join('ü');
+      break;
+    case 'asc':
+      encoding = 'ascii';
+      chunk = new Array(len + 1).join('x');
+      break;
+    default:
+      throw new Error('invalid type: ' + type);
+      break;
+  }
+
+  server();
+}
+
+var net = require('net');
+
+function Writer() {
+  this.received = 0;
+  this.writable = true;
+}
+
+Writer.prototype.write = function(chunk, encoding, cb) {
+  this.received += chunk.length;
+
+  if (typeof encoding === 'function')
+    encoding();
+  else if (typeof cb === 'function')
+    cb();
+
+  return true;
+};
+
+// doesn't matter, never emits anything.
+Writer.prototype.on = function() {};
+Writer.prototype.once = function() {};
+Writer.prototype.emit = function() {};
+
+function server() {
+  var writer = new Writer();
+
+  // the actual benchmark.
+  var server = net.createServer(function(socket) {
+    socket.pipe(writer);
+  });
+
+  server.listen(PORT, function() {
+    var socket = net.connect(PORT);
+    socket.on('connect', function() {
+      bench.start();
+
+      socket.on('drain', send)
+      send()
+
+      setTimeout(function() {
+        var bytes = writer.received;
+        var gbits = (bytes * 8) / (1024 * 1024 * 1024);
+        bench.end(gbits);
+      }, dur * 1000);
+
+      function send() {
+        socket.cork();
+        while(socket.write(chunk, encoding)) {}
+        socket.uncork();
+      }
+    });
+  });
+}