GPU Performance questions

[altcoin]

I usually use stk on a computer with dual gpus. (Intel 4th Gen Integrated Graphics and Radeon HD 8870M)
When I run stk (with all graphics options at max) on my default (less powerful) gpu, the bottleneck appears to be the gpu. FPS are about 20, stk uses ~9% of one cpu core.
When I run stk (with all graphics options at max) on my additional (much more powerful) gpu, the bottleneck appears to be the cpu instead. FPS are only about 30, but stk uses 100% of one cpu core.
While the Vulkan driver is much faster (60 FPS at 30% of one cpu core), I don't think it is a fair comparison because many graphics features are automatically disabled due the the limitations and age of the gpu.

Is the bottleneck on the powerful gpu the limit at which one cpu core can transfer data to/from the gpu?
Is this related to Why SuperTuxKart struggles with 10k scene nodes in a scene, where they discuss the cpu/ram bandwidth saturation?

I usually run stk in 2 or 4 multiplayer and turn down the graphics. Otherwise is lags to 10-20 FPS on gl driver and powerful gpu with visible stuttering of the screen. I think the powerful gpu should be able to handle it somewhat faster if it were not for the cpu bottleneck.

[benau]

Because gl drivers use busy waiting in cpu for each frame synchronization

[altcoin]

Because gl drivers use busy waiting in cpu for each frame synchronization

I see.

Is there any reason that the gl driver on the powerful gpu uses 10 times the cpu and only increases the framerate by half, when compared to the gl driver on the less powerful gpu?

[QwertyChouskie]

What exact CPU do you have?

[altcoin]

What exact CPU do you have?

Intel Core i7-4900MQ

[QwertyChouskie]

What exact CPU do you have?

Intel Core i7-4900MQ

That isn't a particularly low-performance CPU, I suspect it's throttling because of thermal issues. I would highly recommend opening the laptop, cleaning the fans and heatsinks, and replacing the thermal paste. A laptop of this age is very likely to have dry, crusty thermal paste and clogged heatsinks.

[altcoin]

That isn't a particularly low-performance CPU, I suspect it's throttling because of thermal issues.

That is a very good point. My CPU doesn't seem to run too hot, (compared to another I recently cleaned) but it would definitely be worth a try.