Comment by AaronFriel

It's a downside of the "everything is a file" mindset. As all abstractions are, it's leaky.

Nagle's algorithm is elegant because it allows poorly written applications to saturate a PHY.

Disabling it requires the application layer to implement its own buffer.

If I had a time machine and access to the early *nixes, I'd extend Nagle's algorithm and the kernel to treat fsync() as a signal to flush immediately.