>> I agree, but both points are addressed by sendfile()
>
> I'm talking about send(), not sendfile().
> Please remember that send() will be used as the default on Windows or when non-regular files are passed to the function. My argument is about introducing an argument to use specifically with send(), not sendfile().

Which makes even less sense if it's not needed for sendfile() :-)
I really don't see why we're worrying so much about allocating 8K or
16K buffers, it's really ridiculous. For example, buffered file I/O
uses a default block size of 8K. We're not targeting embedded systems.