title: Yarn shows more resources than cluster have
body: <p>I start an EMR cluster with 3 m3.xlarge instance (1 master &amp; 2 slaves) and i have some troubles. </p>
  
  <p>From aws documentation a m3.xlarge instance has 4 vcpu ( <a href="https://aws.amazon.com/ec2/instance-types/" rel="nofollow noreferrer">https://aws.amazon.com/ec2/instance-types/</a> ) . What does it means? This means 4 threads or 4 core with 2 thread each core? I ask you that, because when i open hadoop UI(port 8088) appear to be 8 available vcore per instances, but from what i experienced, cluster behave like a 2 instances with 4 vcore per instances. Am i wrong? Or it's a bug from Amazon or yarn?</p>