Re: Any idea about what makes Emacs slow reading on pipes?

[Richard Stallman]

    We might change it so that, after stashing the stuff in a buffer,
    Emacs looks again if more data is available from the same process.
    If so, also read it and stash it in the buffer, too.

That is worth trying--it might not be too hard to write.  But I think
the problem is in Linux, so the real solution is to change Linux.