message: Use Swoole Process.
diff: #!/usr/bin/env php
  <?php
  -$wait = new Swoole\Atomic(0);
  -$pid = pcntl_fork();
  -if ($pid === 0) {
  +$process = new Swoole\Process(function (Swoole\Process $process) {
  $http = new Swoole\Http\Server('127.0.0.1', 9501, SWOOLE_BASE);
  $http->set(['log_file' => '/dev/null', 'log_level' => SWOOLE_LOG_INFO, 'worker_num' => swoole_cpu_num() * 2]);
  - $http->on('workerStart', function () use ($wait) { $wait->set(1); });
  + $http->on('workerStart', function () use ($process) { $process->write('1'); });
  $http->on('request', function (Swoole\Http\Request $request, Swoole\Http\Response $response) {
  $response->end('<h1>Hello Swoole!</h1>');
  });
  $http->start();
  -} else {
  - $wait->wait();
  +});
  +$process->start();
  +$process->read(1);
  System('ab -c 128 -n 100000 -k http://127.0.0.1:9501/ 2>&1');
  - Swoole\Process::kill($pid);
  -}
  -Swoole\Event::wait();
  +Swoole\Process::kill($process->pid);
  