On Thu, Mar 1, 2012 at 6:59 PM, Eric Dumazet [off-list ref] wrote:

Le 1 mars 2012 08:02, Luiz Augusto von Dentz [off-list ref] a écrit :

quoted

Contrary to someones believes I don't think AF_INET is that fast (e.g.
http://scottmoonen.com/2008/04/05/a-performance-comparison-of-af_unix-with-loopback-on-linux/)

Oh you mention a recent zork it seems ;)

Are we speaking of performance problems, apart from scheduler problems
for D-Bus (each message wakeing all receivers, all receivers read and
drop message but the target) ?

Hi Eric,

The only performance problem we are talking about is the scheduling
for D-bus (context switch to the daemon for each message). With today
implementation the receivers only gets messages that were sent to it
but the D-bus daemon has to be wake it up for every message to he can
do the routing. For multicast messages (i.e: D-bus signals) this is
even worse since the daemon has to do a send() for each receiver.

I am actually one of the few people working to improve performance on
both AF_INET and AF_UNIX parts. Just take a look at recent commits.

Right now you can send/receive millions of udp messages per second on
your linux machine, if you figured out how to avoid process scheduler
costs. If D-Bus wants more, I highly suggest using shared memory
instead of passing messages.
--

Yes, I also thought that AF_UNIX would be more efficient than AF_INET
but I was wrong. Yesterday I wrote some tests using our multicast unix
socket, UDP multicast over IP on a single machine and even multicast
using AF_NETLINK sockets and got very similar performance results.

The only problem is the ordering and control flow requirements for D-bus.

Best regards,
Javier