"H. Peter Anvin" [off-list ref] writes:
If you have an ssh connection, you're writing over a pipe to the ssh
process, and your local buffer is that pipe, which is PIPE_BUF size.
I vaguely recall there was an interesting regression in recent
kernel history when the implementation of the pipe buffer was
changed, with which, writing the same amount of data with
different number of writes made things behave differently and
making the worst case buffer size less than traditional 4K.
I wonder if we are going to be bitten by that one...