Hi Carsten,
On 05/19/2014 06:54 AM, Michael Kerrisk (man-pages) wrote:
On 05/17/2014 03:13 PM, Carsten Andrich wrote:
Hello again everyone,
roughly 3 weeks ago the aftermath of an actually minor patch to fix an
inaccuracy in packet.7's PACKET_TX_RING-related documentation led me to
offer improving the entire PACKET_{RX,TX}_RING-documentation.
Since I do happen to have most of my spare time back by now, I'd like to
tackle this effort before I change my mind :)
Thanks for following up!
On 04/24/2014 12:21 PM, Michael Kerrisk (man-pages) wrote:
I'd leave that plan largely to you. It sounds like Willem and
Daniel are willing to help out.
I'd like to start with getting packet.7's documentation of
PACKET_{RX,TX}_RING into a shape, that should allow most readers to
actually use it without consulting packet_mmap.txt. The latter can be
quite confusing for those unfamiliar with PACKET_{RX,TX}_RING.
I plan to do the following to packet.7:
0. Perhaps a general writeup on how the RX/TX_RING works in Linux,
it's layout, constraints etc. Btw, not sure if that's also
included already, but the same mmap-technique exists also for
netlink sockets.
1. Increase detail of PACKET_{RX,TX}_RING socket options, including
description of struct tpacket_hdr and anything else required to
operate the ring.
2. Move some details from other sockopts (e.g. PACKET_LOSS) into
*_RING.
3. Add fully functional example source code for simple
PACKET_{RX,TX}_RING operation (initialization and operation).
This may be as much as 3 different example programs if I
incorporate [2] and [3] in an appropriate manner. It might be a
good idea to add a non-*_RING example as well.
Yes, some examples for mmap RX, mmap TX, fanout, and perhaps TPACKET_V3
might be great.
4. Add a warning about inferior _TX_RING performance [1] which I
suffered from only recently in the measurements I made for my
thesis on Linux 3.14.
Can you elaborate? Jesper made recently a nice summary on using trafgen
which uses TX_RING internally:
http://netoptimizer.blogspot.ch/2014/04/trafgen-fast-packet-generator.html
5. Other minor changes that'll come up while taking care of 1 thru
4 :)
Absolutely, perhaps explaining differences from TPACKET_V1 -> V3 API and the like.
Any suggestions regarding this rough course of action?
Well, I can't speak to the fine technical details, but the plan looks
rational to me. Perhaps Neil, Willem, or Daniel has a comment.
Just by the way, I suggest CCing netdeve@xxxxxxxxxxxxxxx on all patches.
It may be that someone else also comments.
Cheers,
Michael
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