sendfile(2) SF_NOPUSH flag proposal

[Terry Lambert]

Igor Sysoev wrote:
> > will result in you sleeping with PRUS_MORETOCOME set, but with
> > no more being sent because the send buffer doesn't get emptied,
> > as it's waiting for more data to send.
> 
> But as I understand PRUS_MORETOCOME is not set if socket is non-blocking.

Then the bug is still not fixed by setting it, since your total
send size might be less than `sysctl net.inet.tcp.sendspace`.

You guys should really just have a buffer finalize function
that gets called on block/return cases, and impute the flags
you need on the socket while it's being used for sendfile.

-- Terry