Bing Jiang You suggest jemalloc for memstore block allocations. What are you thinking we'll see by way of benefit? I'd think that isolating the MemStore and then in a simple testing harness trying various options would be the way to go (MemStore can be stood up outside of a HStore IIRC). Try netty implementation first since code is done. See if you can get any speedup in your testing rig. If improvement, then lets talk. We'll have to see about what Nick Dimiduk reminds us of, that netty implemenation is ByteBuf-based (as opposed to ByteBuffer).
On pulling in netty4, it might not be too bad since they changed the package from org.jboss to io.netty.