Re: [Fwd: [Fwd: Is sendfile all that sexy? (fwd)]]

[Ingo Molnar]

On Wed, 17 Jan 2001, Linus Torvalds wrote:

> (I also had one person point out that BSD's have the notion of
> TCP_NOPUSH, which does almost what TCP_CORK does under Linux, except
> it doesn't seem to have the notion of uncorking - you can turn NOPUSH
> off, but apparently it doesn't affect queued packets. This makes it
> even less clear why they have the ugly sendfile)

this is what MSG_MORE does. Basically i added MSG_MORE for the purpose of
getting perfect TUX packet boundaries (and was ignorant enough to not know
about BSD's NOPUSH), without an additional system-call overhead, and
without the persistency of TCP_CORK. Alexey and David agreed, and actually
implemented it correctly :-)

basically if MSG_MORE is not set that means an explicit packet boundary in
the noncontended scenario. If MSG_MORE is set then that means all full-MSS
packets are queued, partial packets are not queued (but are timing out).
sendfile() uses the more flag internally - i've changed sendfile() in my
tree to specify the more flag from higher levels as well - eg. if a sent
file is embedded into other replies, or multiple files are sent.

	Ingo