Github user zhijiangW commented on the issue:
https://github.com/apache/flink/pull/4509
@NicoK , I divided the original `testRequestAndReturnFloatingBuffer` into
three separate tests 'testAvailableBuffersLessThanRequiredBuffers`,
`testAvailableBuffersEqualToRequiredBuffers` and
`testAvailableBuffersMoreThanRequiredBuffers`.
And verifies the following behaviors among them:
1. Recycle the exclusive buffer
2. Recycle the floating buffer
3. Decrease the backlog ---
