Low level CPU-related optimisation is absolutely still a thing. The GPU is always filled to the brim trying to get as much quality out of a graphics frame so a lot gets offloaded to the CPU. When I was doing this I was doing a lot of low-level CPU optimisation. GPU optimisation was usually more about transform process topology but there was plenty of low-level work to do there too.
Games are both high throughput AND low-latency and C++ is still king there
Games are both high throughput AND low-latency and C++ is still king there