Lag

Lucifer sez

Fix the internet.

As flippant as that is, it is the source of lag. We've experimented (we as in "server admins") with a number of solutions over the last year or so (and I assume it was happening earlier) and here's what we've found, near as I can tell.

If the machine is dedicated to the armagetron server, it will have less lag. Even my server has some interesting lag effects whenever it receives mail (it's a mail server too), and that's with the armagetronad process reniced to a low level (-15 I think it is).

If the machine is on a slow processor with a small cache, it will have more lag. This effect is amplified if the machine is not dedicated to the game and/or if you run more than one game server.

Lag is reduced by parallel processing on the server, so if you have a fancy Xenon processor or a dual proc setup you can have less lag.

Lag is reduced by running a 2.6 Linux kernel over *any* other kernel (Windows, Linux 2.4, I dont' know that any others have been tested in this way). It can probably be reduced even further by applying the low-latency patches, but since those are mostly used for audio work I don't know how well they'd work here.

The closer the server is to the backbone, the less lag. The closer the client is to the backbone, the less lag the client has. (I'm pretty far from it, hence the high pings on teh Crack Pipe, but they do look better than they used to be)

After you've done all of this, the lag will be noticeably less, but there will still be numerous complaints. This is because the internet itself is the source of all lag. So all of these measures only decrease the roundtrip time for a packet that has already crossed the internet and reached the machine.

There have been a number of improvements in this area. 0.2.7.1 had simulation improvements, and also an improvement where the server can be anchored to a certian number of simulation steps per minute. So that's why 0.2.7.1 servers have more predictable lag than older servers, and when everyone is connected with newer clients, you can really see the difference. 0.2.8_beta2 has a major network refactoring that also seems to reduce lag, even though it may not be noticeable in your ping. I don't know that it would be noticeable in your ping, and since there aren't yet that many servers running the new betas the only measure I have is my own, which has less lag than the older version.

The only improvements I can think of would be to optimize code here and there, and I don't even know which code needs to be optimized. I know that periodically some one or more developers profile various pieces of code and that there has been optimizing. I also know that most of the developers around here think about performance while coding. ANd I also know that there is code that is not well optimized (although I can't point to any specific line, if I could do that, I could optimize it, right?).

So let's assign a value, C, which represents how much work is required to thoroughly optimize the code and reduce latency to bare minimum while retaining reliability and accuracy. Now let's assign a value, T, which represents how much time the entire development team has to dedicate to exactly that. Let's assign one more variable that represents how long before really fast internet arrives in everyone's houses (faster than even broadband now) and includes faster processors, faster network cards, and generally very low latency on the hardware end. We'll call this one H, for "toy".

C / T > H

Smile

(The purpose of this post is to try to get people to realize that lag is part of the game and the best thing you can do to reduce the effect of lag on your game is to adapt to it as much as possible. Now cue Jonathan, who recently cleaned my clock while suffering insane lag on his end while I had pings below 20ms on mine....)