In nioBuffer(int,int) in CompositeByteBuf , we create a sub-array of nioBuffers for the components that are in range, then concatenate all the components in range into a single bigger buffer.
However, if the call to nioBuffers() returned only one sub-buffer, then we are copying it to a newly-allocated buffer "merged" for no reason.
Motivation:
Profiler for Spark shows a lot of time spent in put() method inside nioBuffer(), while usually no copy of data is required.
Modification:
This change skips this last step and just returns a duplicate of the single buffer returned by the call to nioBuffers(), which will in most implementation not copy the data
Result:
No copy when the source is only 1 buffer
0bea8ecf5d