BufferPool manages several pools of direct-memory ByteBuffers. When asked for a ByteBuffer of size X you may receive a buffer that is any size greater than or equal to X. For users of this pool this is unexpected behavior and is causing some trouble.
MessageStreamer, for instance, performs message "chunking" based on the size of a socket's buffer size. It requests a byte buffer of that size and then fills it over and over again with message chunks to be written to the socket. But it does this based on the buffer's capacity, which may be much larger than the expected buffer size. This results in incorrect chunking and requires larger buffers in the receiver of these message chunks.
BufferPool should always return a buffer that has exactly the requested capacity. It could be a slice of a pooled buffer, for instance. That would let it hand out a larger buffer while not confusing the code that requested the buffer.