[Patch Request] dmemcg VRAM priority patches (v6) — fix VRAM eviction order for gaming

[thekk1]

Summary

Requesting inclusion of Natalie Vock's (pixelcluster, Valve contractor) dmemcg
patch series (v6) into the Bazzite kernel. These patches fix a longstanding
VRAM management issue in the Linux kernel where background applications can
displace game data from VRAM into the slower GTT region (system RAM via PCIe),
causing stuttering and performance degradation.

Problem

On systems with ≤8GB VRAM (e.g. RX 9060 XT, RX 7600, Steam Deck), the kernel
has no mechanism to prioritize which process's GPU memory allocations are
protected from eviction. A browser with many open tabs can cause game assets to
be evicted to GTT even while VRAM is partially free for lower-priority
processes. This results in gradual performance degradation during gaming
sessions.

The same issue affects the Steam Deck: while it uses unified memory physically,
the kernel and userspace treat VRAM and GTT as separate pools. Unnecessary
data movement between these pools causes real overhead that these patches
eliminate.

Solution

Six kernel patches modifying TTM allocation/eviction logic and adding DRM
device memory cgroup (dmemcg) controller support, combined with two userspace
utilities:

• dmemcg-booster — systemd service that enables/configures dmem cgroup
  controllers to activate VRAM protection
• plasma-foreground-booster — integrates with KDE Plasma to give the
  focused/foreground application (typically a game) highest VRAM priority;
  alternatively, newer Gamescope versions also support this

Measured Impact

In testing with Cyberpunk 2077 on an 8GB GPU:

• VRAM utilization: ~6 GB → ~7.4 GB (+23%)
• GTT spillover: 1.37 GB → 0.65 GB (−53%)

Patch Links

• Blog post / technical writeup: https://pixelcluster.github.io/VRAM-Mgmt-fixed/
• Phoronix coverage: https://www.phoronix.com/news/Valve-Better-Gaming-Low-vRAM
• Patch series on lore.kernel.org: linked in the blog post above (section
  "How do I use this?")

Current Adoption

• CachyOS: included since kernel 7.0rc7-2, also in 6.19.12
• Liquorix: included since 6.19-9
• Bazzite: not yet included (this request)

Notes

• Patches apply cleanly on top of 6.19.x
• Requires accompanying userspace packages (dmemcg-booster,
  plasma-foreground-booster) — these would need to be added to the Bazzite
  image separately, but the kernel side is the prerequisite
• The developer has noted the patch is still pre-mainline; once upstreamed
  into mainline Linux it will arrive automatically, but inclusion in
  kernel-bazzite in the meantime would benefit users on ≤8GB AMD GPUs and
  Steam Deck users significantly