Hello Andre,
A couple of things if you're poking around in this area...
On 10/18/12 13:44, Andre Oppermann wrote:
On 18.10.2012 22:22, Andre Oppermann wrote:
Author: andre
Date: Thu Oct 18 20:22:17 2012
New Revision: 241703
URL: http://svn.freebsd.org/changeset/base/241703
Log:
Remove double-wrapping of #ifdef ZERO_COPY_SOCKETS within
zero copy specialized sosend_copyin() helper function.
Note that I'm not saying zero copy should be used or is even
more performant than the optimized m_uiotombuf() function.
Some time back I played around with a modified m_uiotombuf() that was
aware of the mbuf_jumbo_16K zone (instead of limiting itself to 4K
mbufs). In some cases it performed better than the stock m_uiotombuf.
I suspect this change would also help drivers that are unable to deal
with long gather lists when doing TSO. But my testing wasn't rigorous
enough (I was merely playing around), and the drivers I work with can
mostly cope with whatever the kernel throws at them. So nothing came
out of it.
Actually there may be some real bit-rot to zero copy sockets.
I've just started looking into it.
I have a cxgbe(4)-specific true zero-copy implementation. The rx side
is in head, the tx side works only for blocking sockets (the "easy"
case) and I haven't checked it in anywhere. Take a look at
t4_soreceive_ddp() and m_mbuftouio_ddp() in sys/dev/cxgbe/t4_ddp.c.
They're mostly identical to the kernel routines they're based on (read:
copy-pasted from). You may find them of some interest if you're working
in this area and are thinking of adding zero-copy hooks to the socket
implementation.
Regards,
Navdeep
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