Beyond the limits of physical VRAM

Earlier this year, Natalie Vock made a splash with a set of patches to the Linux kernel that greatly increased performance on AMD GPUs with lower amounts of VRAM. With that work now accepted by upstream, Vock decided to turn their attention to another interesting problem: what if you run out of VRAM, and how can we improve performance when we do?

Regardless, what I hope this blogpost can demonstrate is that even if you end up with some memory evicted to system RAM, the slowdown can be manageable. There’s measures that drivers (particularly, the kernel driver) can take to make overcommit work as fast as possible, and even applications can do their part in coordinating with the driver stack to mitigate the effects of their memory being evicted. With everything in place, VRAM overcommit isn’t really as big of a deal as one may think it is at first sight. ↫ Natalie Vock

The work Vock has done has already been in SteamOS for a while, and they’re currently in the process of upstreaming it to the vanilla kernel as well. Since this is a complex set of patches and changes, this may take a while, and as such, they’ve prepared custom kernel and Mesa branches for adventurous users. Do note that these branches won’t be maintained much, and are entirely experimental, not as well-tested as the SteamOS kernel, and probably won’t yield the same performance improvements.

Still, this is the kind of work that has a material impact for users. Not everyone has a 16GB monster GPU, especially not today with supply chains ravaged and ruined by slopmakers, so it’s great to see the Linux world working to improve performance for everyone, not just the wealthy few.