You can also use TCP_CORK to reduce the number of packets without any increased latency.
Disabling TCP_NODELAY would also reduce number of packets + be portable & simpler to implement - but would incur a latency penalty.
Disabling TCP_NODELAY would also reduce number of packets + be portable & simpler to implement - but would incur a latency penalty.
For people who don't feel like googling it:
1. You TCP_CORK a socket
2. You put data into it and the kernel buffers it
3. If you uncork the socket, or if the buffer hits MSS, the kernel sends the packet
Basically, the kernel waits until it has a full packet worth of data, or until you say you don't have any more data to send, and then it sends. Sort of an extreme TCP_YESDELAY.
See https://catonmat.net/tcp-cork for where I learned it all from.
I am aware of TCP_NODELAY (funny enough I recently posted about TCP_NODELAY to HN[1] when I was thinking about it for the same game that I wrote about here). But I think the latency hit from disabling it just doesn't work for me.
I got a kick out of this comment [0]. "BenjiWiebe" made a comment about the SSH packets you stumbled across in that thread. Obviously making the connection between what you were seeing in your game and this random off-hand comment would be insane (if you had seen the comment at all), but I got a smile out of it.
"hello world" fits in a single TCP packet, but the kernel might end up sending one packet containing "hello" and another packet containing " world". It is completely opaque to userspace.
TCP_CORK lets userspace decide when packets are dispatched. You get to control whether "hello world" is sent across 1 packet or 11 packets.
Ah, maybe you are saying it doesn’t help the situation in the post. That’s what I misunderstood.