title: PooledUnsafeDirectByteBuf not found in DirectMemory
body: <p>I am using Netty 4.1.17-Final.</p>
  
  <p>I wrote the code to send and receive 100 MB random ASCII. Decoder does not read until ByteBuf becomes 100 MB.</p>
  
  <pre><code>@Override
  public void decode(ByteBuffer _in, List&lt;Object&gt; _out) {
      if (_in.remaining() == size) {   // size = 100 * 1024 * 1024
          _in.get(new byte[size]);
      }
  }
  </code></pre>
  
  <p>Therefore, Netty buffers 100 MB, but it was not found even by monitoring Direct Memory.</p>
  
  <pre><code>System.out.println(sun.misc.SharedSecrets.getJavaNioAccess().getDirectBufferPool().getMemoryUsed());
  ManagementFactory.getPlatformMXBeans(BufferPoolMXBean.class).forEach(buf -&gt; {
      System.out.printf("%s: Used=%d, TotalCap=%d%n", buf.getName(), buf.getMemoryUsed(), buf.getTotalCapacity());
  });
  
  // Result
  // 10
  // direct: Used=9, TotalCap=8
  // mapped: Used=0, TotalCap=0
  </code></pre>
  
  <p>Netty used PooledUnsafeDirectByteBuf, but where do you buffer the received data? Or is the direct buffer monitoring method incorrect?</p>