[_wmd]

I'd have presumed otherwise, but I'm not sure if you're understanding the API correctly.. it's not about sending multiple messages to the same destination, but to multiple destinations in a single call. The msg_hdr struct has room for specifying the target address.

From userspace' perspective, even if the same data isn't being broadcast at every client, just building up a big array (perhaps while looping over the input from recvmmsg()!) and spitting it out once would have the same semantics as just calling sendmsg() immediately on each, etc

[jacquesm]

Yes, I understand the API correctly. Having implemented it once I think I have the basics down ;) But that said I was assuming that this would be in the context of multiple UDP messages sent from a game client to a game server.

[Doxin]

The bottleneck generally isn't at the client side for games, The server has much more network traffic to handle. So even if this performance fix only works server-side that might be enough.