[6.18] Track gaming patches

[kakra]

Export patch series: https://github.com/kakra/linux/pull/44.patch

Gaming und Desktop Interactivity Patches

This is a combined patchset from various sources, including some ports of old legacy Proton features (deprecated). The patchset mostly focuses around memory management and interactivity, optimizing the system for responsiveness rather than maximum throughput, to reduce stutters, memory thrashing and frame drops. Most unrelated ZEN patches have been dropped.

Changes since 6.12 LTS

• ntsync: dropped because it's upstream now (you may need to add a udev rule ACTION=="add|change", KERNEL=="ntsync", SUBSYSTEM=="misc", MODE="0666" to set proper permissions)

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Included Patches

• Selected ZEN interactive patches: memory management, interactivity, gaming defaults, disk scheduler defaults
• Threaded IRQs by default: cherry-picked from CK for better responsiveness
• Prefer full idle SMT cores: prefers idle CPU cores for better throughput and better response times
• BORE scheduler from CachyOS: ignores ZEN interactive if enabled (https://github.com/firelzrd/bore-scheduler)
• ADIOS IO scheduler from CachyOS: The "Adaptive Deadline I/O Scheduler", optimized for latency instead of throughput should reduce load stutters in games, this overrides the ZEN default for BFQ if enabled

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Recommendation

Kernel 6.18 LTS seems to have worse performance characteristics for games compared to kernel 6.12, especially frame pacing can jitter a lot more, resulting in reduced perceived smoothness despite average FPS being identical or better. I found that I can fix it by building the kernel with support for sched_ext, and then running with the LAVD scheduler which also yields lower power consumption when idle (sys-app/kernel in Gentoo):

CONFIG_BPF=y
CONFIG_BPF_JIT=y
CONFIG_BPF_JIT_ALWAYS_ON=y
CONFIG_BPF_JIT_DEFAULT_ON=y
CONFIG_BPF_SYSCALL=y
CONFIG_DEBUG_INFO_BTF=y
CONFIG_FUNCTION_TRACER=y
CONFIG_KPROBE_EVENTS=y
CONFIG_SCHED_CLASS_EXT=y

Here's a talk on the technical details of the LAVD scheduler which initially has been made for the Steam Deck: https://www.youtube.com/watch?v=5F-vQgv4sI0

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Deprecated

• FUTEX wait multiple opcode 31: most likely only used by old Proton versions, will be dropped with the next LTS

Dropped

• Soft dirty flag with reset: dropped during the rebase because it no longer applied cleanly. Modern Wine/Proton uses the newer writewatch/userfaultfd path instead, so this old soft-dirty implementation is no longer needed.

[kakra]

Added note about performance characteristics to the top post:

Kernel 6.18 LTS seems to have worse performance characteristics for games compared to kernel 6.12, especially frame pacing can jitter a lot more, resulting in reduced perceived smoothness despite average FPS being identical or better. I found that I can fix it by building the kernel with support for sched_ext, and then running with the LAVD scheduler which also yields lower power consumption when idle (sys-app/kernel in Gentoo)

[kakra]

Added Adaptive Deadline I/O Scheduler (ADIOS) from CachyOS. It is optimized for latency instead of throughput and should reduce load stutters in games but also improve general desktop responsiveness. This overrides the ZEN default for BFQ if enabled.

[kakra]

Rebased to v6.18.3 to resolve conflicts.

[kakra]

Rebased to v6.18.18 to resolve conflicts.

[kakra]

Rebased to 6.18.33 to resolve conflicts.

[kakra]

Rebased to 6.18.46: Two older soft-dirty patches were dropped during the rebase because they conflicted. Modern Proton/Wine no longer relies on that soft-dirty path, so this should not affect current users.