> One reason for a smaller PIPE_BUF is that you cannot wake up any threads
> write-selecting on a pipe until PIPE_BUF bytes are available in the pipe.
> If PIPE_BUF is large, then you run the risk of increasing the latency of
> writes to the pipe, yes?

Does Posix say that?
I didn't see any refererence to PIPE_MAX in the posix select man page.

In any case it definitely says that a write of more that PIPE_MAX
can return having put less that PIPE_MAX bytes into the pipe.
(indeed a test suite may decide to test for such behaviour, and
(I think) assume that reading a byte implies that a byte can be written).

	David

-- 
David Laight: david@l8s.co.uk