Using the intermediate buffer on the read side allows the kernel buffer to act as a 「readahead cache」 when the application hasn't asked for as much data as the kernel buffer holds.
The intermediate buffer on the write side allows the write to complete asynchronously.
在写入方面的中间缓沖区则可以让写入过程异步完成。
In order to assure that worshippers are not disturbed, the hotel-restaurant has been separated from the religious buildings by means of an intermediate buffer space.