KAG Why does KAG eats so much CPU?

KAG can only use one core, so a server is bad if it has 6 weak cores.

 

It uses 100% of 1 core.

 

No. I can (unfortunately) fairly confidently say that KAG will never be extensively multithreaded.

Rewriting code that has been designed to run in serial (ie not multithreaded) in a parallel way (ie multithreaded) is a nightmare. If the engine had been programmed with multithreading in mind, then sure, but threading isn't some pixie dust you throw at the code and it suddenly runs three times as fast; it opens you up to a whole new subset of possible bugs which are much harder to debug, and getting code running portably is harder. Unless the threading is ubiquitous and well planned, it's also not often much faster, as a lot more time is spent checking locks, switching contexts, waiting on other threads to finish, etc.

The only thing that's currently threaded in KAG is the API code. Incidentally, the API code has been identified as a likely candidate for the recent "every server lags" issue. Read into that what you will :^)

 

I would not do either of those things - disabling compression will mean your network usage will be up to five times as high, fast deltas is legacy functionality that will both expand usage and may result in crashing.

Possible CPU Savers:

Decrease your player count
Host smaller maps
Host maps without water
Host gamemodes without siege
Host gamemodes without explosives
Decrease the amount of "scenery" blobs on your map (bushes, fish, trees) as this will reduce the amount of work box2d has to do


Incidentally, You can host a heap of separate kag servers on a multi-core box without them affecting each other's performance.

Hardmode:
Write a gamemode that passes people between several hosted, unlisted servers ("realms"), which would all run separate maps. You can do this by getting them to evoke CNet::Connect with an IP and port from the listed "master" server, and when going through "portals" or off the edge of the map, or however you want them to move around. This would both alleviate your overloading-one-core issue and make your server very unique :^)

Re: Is it possible to "optimise" to run on multiple cores -
No, running on multiple cores at the same time is what multithreading is. It is possible for us to optimise how the game runs on one core, but you'd be surprised how much of that we've already done. Most of the CPU usage currently comes from libraries (angelscript and box2d, sometimes irrklang but not on the server) which are much harder for us to optimise (we have to rewrite other people's code rather than our own). It's not likely for us to do much of that other than fixing the current "omg server lags forever" bug which is being investigated this week.

 

Server lag can cause multiple different problems. Bombs exploding too late, people respawning too late, ping spikes, kicking everyone on mapchange, etc.

 

Just make sure your server never gets stuck on 100% cpu load....