The writev filter method performs the same function as the write filter method, but the format of its parameters is different. You do not have to implement the writev filter method. If a filter implements the write filter method but not the writev filter method, the server uses the write method instead of the writev method. A filter should not implement the writev method unless it also implements the write method.
Under some circumstances, the server may run slightly faster when filters that implement the write filter method also implement the writev filter method.