[2020] CPU optimization is something we should care more about

If you are bouncing between 70fps and 150fps, do you have "Wait For Vertical Sync" on? That can cause the game to drop from the monitor's frame rate to half that whenever the CPU dips even slightly below the monitors frame rate.

He's right. That's not the way that Multi core CPUs work. A single thread will not run on just one core - it will jump across different cores, one at a time. On an 8 core system, one thread running at 100% can and probably will) look like 12.5% of your entire system. One individual core will not run flat out while the others are idling.

Hi, I'm Tony and I'm a Rioter and I care about your FPS.

This is something we are working on and will continue to. We are constantly improving and updating League and a side effect of that is that things slow down as more things get added to the game. As we detect these slowdowns (ideally we catch these problems before they go live), we fix them, but sometimes the changes are so small, no one notices them. And when we have 100s of changes going in and some of them are imperceptibly slower, we can end up with a noticeable slow down with no obvious cause. It's death by a thousand paper cuts. These are hard to fix. All we can do is look at the performance of the game and look at the slowest parts, then try and optimise them. And we've already fixed all the low hanging fruit.

To optimise something, we first need to measure it. We've been sneakily adding in a lot of new performance measuring capabilities into the LIVE game so that we can accurately measure the performance players have in game, so we can fix those problems.

For example, if you looking in your "Logs/Performance Logs" directory in your League install directory, you'll see a file ending in ".rpd". This is a Riot Performance Dump. It contains detailed information on the performance of your most recent game. If you have a game which has subpar performance, you can should be able to send that file to Player Support. Then someone like me can look at it, see if there is something particularly odd going on with your machine (which sometimes happens) or whether it is part of the endemic performance issues we're monitoring and addressing.

We're also collating a lot more information from every game played so that we can see how the game performance trends globally - what we collected before was better than nothing, but as of the next patch we'll have a whole lot more.

We know that performance has been degrading with recent patches. We're not ignoring that - we're trying to figure out why so that we can fix it. The first part is measurement. The second part is addressing the parts which are slow - optimisation.

Your patience and support is appreciated - threads like this can help us highlight some issues that we can't reproduce ourselves, so don't stop talking about this. Tell us when things get better and when they get slower.

You'll probably notice that nothing is at 100%, yet you're not able to hit an fps cap. That isn't supposed to happen.

Yeah, it is. A single thread doesn't lock to a single core - it will run on whatever core the system deems appropriate. If you run a single thread flat out, constantly, it will not use up one Core 100%, it will spread across all the available cores. If you have 8 cores, you'll see 12.5% utilisation.

I think the underlying concern here is that League isn't "Multi-threaded" enough. That we should be able to use 100% of all the available cores to maintain 144fps. And that is a fair concern - League does run on multiple threads and also uses multiple threads indirectly, but the core gameplay is mainly run on a single thread.

Now, one of the issues with multi threading is that it can increase latency - we're doing more at once, but all those things that are happening at once cannot be dependent on each other. We can't render something while we're updating its location, and we can't update its location while we're doing its AI, and we can't do its AI until we have an update from the server as to what the world looks like. The common solution in these cases is to defer the processing so that while we're doing the server update for frame N, we're doing the AI for frame N-1, and the location update from frame N-2 and the rendering from frame N-3. In this way, at the cost of more memory and more CPU usage, we can do things quicker, but later. We've increased the latency - it will take more frames for your input to take effect.

That's not to say that multi-threading shouldn't happen (or be better utilised). It just needs to be carefully considered. Only those things which have no dependencies on each other can run in parallel.

Another issue is that we also need to support low spec machines - we can't utilise 8 cores on a 2 core machine. So this all needs to scale as well.

There is a lot more stuff in League now - not just graphical. We're dealing with entirely new systems - new abilities require new code and data. If you could run an old version of League you'd see the difference. It's come a long way.

Yup. That's pretty much it. As long as you have at least 2 cores, running 4 hyperthreads, CPU speed is the determinant factor. At the moment.