This issue tracks merging the code for zero-copy memory-mapped HDFS client reads from the HDFS-4949 branch to trunk and branch-2. This includes the patches originally committed on the feature branch in HDFS-4953 and HDFS-5191.
revisit zero-copy API in FSDataInputStream to make it more intuitive
ElasticByteBufferPool#Key does not implement equals.
enable HDFS local reads via mmap