Messages in this thread | | | Date | Mon, 03 Mar 2003 14:11:07 -0500 | From | Chris Friesen <> | Subject | Re: anyone ever done multicast AF_UNIX sockets? |
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David S. Miller wrote: > From: Chris Friesen <cfriesen@nortelnetworks.com> > Date: Mon, 03 Mar 2003 13:07:45 -0500 > > Suppose I have a process that waits on UDP packets, the unified local > IPC that we're discussing, other unix sockets, and stdin. It's awfully > nice if the local IPC can be handled using the same select/poll > mechanism as all the other messaging. > > So use UDP, you still haven't backed up your performance > claims. Experiment, set the SO_NO_CHECK socket option to > "1" and see if that makes a difference performance wise > for local clients.
I did provide numbers for UDP latency, which is more critical for my own application since most messages fit within a single packet. I haven't done UDP bandwidth testing--I need to check how lmbench did it for the unix socket and do the same for UDP. Local TCP was far slower than unix sockets though.
> But if performance is "so important", then you shouldn't really be > shying away from the shared memory suggestion and nothing is going to > top that (it eliminates all the copies, using flat out AF_UNIX over > UDP only truly eliminates some header processing, nothing more, the > copies are still there with AF_UNIX).
Yes, I realize that the receiver still has to do a copy. With large messages this could be an issue. With small messages, I had assumed that the cost of a recv() wouldn't be that much worse than the cost of the sender doing a kill() to alert the receiver that a message is waiting. Maybe I was wrong.
It might be interesting to try a combination of sysV msg queue and signals to see how it stacks up. Project for tonight.
Chris
-- Chris Friesen | MailStop: 043/33/F10 Nortel Networks | work: (613) 765-0557 3500 Carling Avenue | fax: (613) 765-2986 Nepean, ON K2H 8E9 Canada | email: cfriesen@nortelnetworks.com
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