title: Is the access performance of __constant memory as same as __global memory on OpenCL
body: <p>As I know. Constant memory on CUDA is a specific memory. And it is faster than global memory.
  But in OpenCL's Spec. I get the following words.    </p>
  
  <blockquote>
    <p>The <code>__constant</code> or constant address space name is used to describe variables allocated in global memory and which are accessed inside a kernel(s) as read-only variables </p>
  </blockquote>
  
  <p>So the <code>__constant</code> memory is from the <code>__global</code> memory. Does that mean it have the same accessing performance with the <code>__global</code> memory?</p>