Linux 7.3 improves performance when running out of vRAM

Earlier this year, I blogged about work I did to improve VRAM management for games. Now, after many months of floating around in mailing lists, the kernel patches are finally merged upstream and queued for Linux 7.3! Hooray! To celebrate, let’s look a bit deeper at one sentence I wrote in my previous post: [Games] should perform much more stable - as long as the game itself doesn’t use more VRAM than you actually have. So, one may ask: What if they do, in fact, use more VRAM than you actually have? Typical expectations for this seem to be that once this happens you’re pretty much screwed. Games will start crashing left and right, performance plummets to unplayable levels, a good gaming experience becomes impossible. But is that really just an unavoidable fact of life? What really makes running out of VRAM suck so hard? And, most importantly: How can we make it suck as little as possible? Setting expectations In theory, running out of VRAM should exclusively be a performance issue, not a stability one. Support for overcommitting VRAM has existed for as long as GPU drivers have: If the driver overcommits VRAM, you are generally allowed to request as much VRAM as you’d like, and you’ll get as much as the kernel driver decides it can fit into the physical memory that exists on GPU. On the performance side, the big-picture reason for bad performance when you run out of VRAM is fairly simple. As soon as the game requests more VRAM than is physically present, some of the game’s memo…