javascript - Load testing node.js app on Amazon EC2 instance -

i trying load test node.js application endpoint api hosted on m4.large instance using jmeter 1 master , 3 slaves. 'server.js' file uses clustering in node.js follows:

var c_num_cpu = 2; // listen dying workers  if (cluster.ismaster) {  (var =0; < c_num_cpu; ++)   {     cluster.fork();   }   cluster.on('exit', function (worker) {  // replace dead worker console.log('worker %d died :(', worker.id); cluster.fork();   });   return; } 

when tested keeping 'var c_num_cpu=2', max response time crossed 42s, however, on making 6, response time dropped 1.7s! vcpu m4.large 2, how load being handled? also, in such case, how determine optimal choice of instance?

the issue jmeter slaves. dying due increased response time. solved on increasing number of slaves.