What GPU priority settings in registry actually do

There are two GPU priority settings in Windows that most optimization guides mention but few explain correctly.

GpuPriority in IFEO

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\game.exe\PerfOptions
GpuPriority = 8

This sets the GPU engine priority for threads spawned by the process. Range is 0-8, where 8 is highest. Higher priority means the GPU scheduler prefers this process when deciding what to execute next on the GPU command queue.

On busy systems with overlays, browsers, and other GPU consumers running alongside games, this gives the game priority access to GPU execution time.

GPU Priority in MMCSS

HKLM\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Multimedia\SystemProfile\Tasks\Games
GPU Priority = 8

This is the MMCSS-level GPU priority applied to threads registered under the "Games" MMCSS task. It affects the Windows GPU scheduler independently from the IFEO setting.

Both should be set to 8 for gaming.

What you see

These settings don't typically change average FPS significantly. What changes is consistency — the GPU is less likely to be interrupted by DWM compositing or overlay rendering mid-frame. This shows in frame time graphs as fewer outlier spikes.

IzanagiOP sets both via the Trajectory Pack (per-game IFEO) and HitSync Pack (MMCSS). https://terweb.lt/