Linux 7.3 improves performance when running out of vRAM

Since the introduction of kernel patches in Linux 7.3, games running out of VRAM will experience improved performance stability, provided the game itself does not demand more VRAM than physically available. However, when games consume more VRAM than present, users may encounter crashing games, plummeting performance, and an unplayable gaming experience.

This phenomenon results from the GPU having to access CPU memory, which is significantly slower than VRAM, and must overcome the PCI bus latency. The situation becomes even more severe when data to be accessed exceeds the 1GiB frame limit. However, cache hits can help mitigate some performance losses during CPU memory accesses, as the latency for cache hits remains consistent, regardless of whether data resides on the CPU or GPU.

The reason for the performance impact when running out of VRAM lies in the GPU having to retrieve data from CPU memory, which is inherently slower than VRAM and requires traversing the PCI bus. Cache hits can offset some of the latency costs, as memory accessed from the cache exhibits similar latency, irrespective of the memory location.

Still, precise performance outcomes can vary based on factors such as cache-friendliness, infrequently accessed memory, and allocations with limited data usage. Despite these variables, the overall impact of running out of VRAM on gaming performance remains challenging to predict.