The CPU has a power saving mode that lets it slow down whenever a thread is sleeping (even a few milliseconds). In games, the main thread does short bursts of work then sleeps briefly. So the CPU keeps waking up "cold" at a low speed, causing occasional slow frames (the "1% lows").

The patch adds a window where the CPU won't go into the power saving state immediately, so when the thread starts working again the CPU is at full speed already.

IIUC: Cpu cores can be set to sleep immediately after stopping activity to save energy but takes an amount of time to "wake" so game rendering has a lot of pauses in computations that make this effect less performative but more energy saving. Mobile game devices rely on this for more battery power.

Disabling said sleep would make the core on all the time and not energy efficient.

This change seems to find ways to keep gaming computations that were recently used and will likely happen again very soon, from sleeping too aggressively but still allow sleeping as much as makes sense to balance frame computation and energy efficiency.