Limited by Main Thread but none of the threads are actually maxed out

[WellREDBarron]

I wrote this in another thread yesterday. It might help.

@WellREDBarron

That isn’t a great way to see what the Main Thread is doing.

You might be able to spot issues like a core running at 100% would be a clue as to what is causing a slowdown. Or minimal usage across all cores could be a sign your slowdown is coming from elsewhere and not the CPU… but…

And this is important…

Very important…

The Main Thread is not a CPU, or a CPU core. It is the amount of time it takes ALL cores working together to perform one cycle to calculate data for one frame.

And to this day, even with the best CPUs, it is very likely folks will need to lower their Terrain Level of Detail especially, to get that Main Thread cycle fast enough to meet reasonable FPS requirements, and very tricky to get ultra high fidelity and 60 FPS.

If you are ok with 30 FPS, that can be done on most decent CPUs with a little LOD adjustment. If you want 60 FPS, you need to be prepared to make some real sacrifices. And you still might not get it 100% of the time.

DX11 and 12 do manage CPU efficiency differently and you can see some of those differences in that window, but that is not your Main Thread.

Again, the Main Thread is the amount of time it takes ALL cores working together to perform one cycle to calculate data for one frame.

So, sometimes a core has to wait for another to finish its calculations to be able to build upon the data generated with its own new calculations. Multiple cores working together often means cores are waiting for other cores. That time spent waiting for ALL cores to communicate, build, and perform the calculations needed to finish a cycle and build that next frame is like lag.

You can see some of this lag in the Developer Mode.