Github user pnowojski commented on the issue: https://github.com/apache/flink/pull/5104 2 times improvement is for network stack only. With other things in play (like even simple operators) it will be smaller. As we discussed offline, I didn't want tightening up the connection/dependencies of `RecordSerializer`. `Buffer` is a much simpler dependency compare to `BufferProvider`. Think how more difficult would it be to test it with `BufferProvider`. However I was thinking about refactoring it in another direction, creating kind of `write-only` `@NotThreadSafe` `BufferBuilder` class. I have create a separate issue for that: https://issues.apache.org/jira/browse/FLINK-8178
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