write(2) takes > 17 seconds even with O_NONBLOCK

[Dieter]

I've always thought that writing to a file descriptor with O_NONBLOCK
set was supposed to return quickly.  Isn't that the whole point of
O_NONBLOCK ?

I have a C program writing to stdout, which is set to O_NONBLOCK,
and the shell redirects stdout to a regular disk file.  Dispite
O_NONBLOCK, my program reports that a write call took 17.701340
seconds.