Enable Transparent Hugepages when Gaming

[sockusminimus]

Transparent Hugepages (THP) have the kernel allocate memory pages in 2MiB or 2GiB units instead of 4KiB units as is the platform default on X86. This has been shown to measurably improve gaming performance in many cases. The risk for enabling this is low, as some distros do this by default (such as OpenSUSE). It is also a kernel tunable that can be set at runtime using sysctl.

I propose we enable THP and disable proactive compaction for gaming sessions and set these back to default when the session ends (as some workloads such as databases can be negatively impacted by memory fragmentation that this can cause).

My proposal is to enable the following when gaming and restore when game ends:
echo always | sudo tee /sys/kernel/mm/transparent_hugepage/enabled
echo advise | sudo tee /sys/kernel/mm/transparent_hugepage/shmem_enabled
echo 0 | sudo tee /proc/sys/vm/compaction_proactiveness
echo 0 | sudo tee /sys/kernel/mm/transparent_hugepage/khugepaged/defrag

See e.g. https://github.com/CryoByte33/steam-deck-utilities/blob/main/docs/tweak-explanation.md
See also https://blog.patshead.com/2023/02/enabling-transparent-hugepages-can-provide-huge-gaming-performance-improvements.html
See also https://alexandrnikitin.github.io/blog/transparent-hugepages-measuring-the-performance-impact/