Pet Farrari wrote:
> Hi,
>
> This is just a quick question, does freebsd (6/6.2) using sendfile(2)
> system call to eliminate the double-copies (normally the file content is
> read into the application then write out to the socket) between
> application and socket?
>

$ man 2 sendfile

....

IMPLEMENTATION NOTES
The FreeBSD implementation of sendfile() is "zero-copy", meaning
that it has been optimized so that copying of the file data is
avoided.
....

and take a look at /usr/src/sys/uipc_syscalls.c round about line 1797...
in particular...


/*
* Loop through the pages in the file, starting with the requested
* offset. Get a file page (do I/O if necessary), map the file page
* into an sf_buf, attach an mbuf header to the sf_buf, and queue
* it on the socket.
*/

It's not the cleanest implementation imaginable but the source is very clear about what's going on!


pete
--
pete@fenelon.com "he just stuck to buying beer and pointing at other stuff"