Hardware-accelerated GPU scheduling (HAGS) is a Windows feature that can cause problems for older or cheaper graphics cards. The feature takes a slice of VRAM that 6GB and 8GB cards can't easily spare. When XDA Developers switched HAGS off on an 8GB RTX 2070 Super, it freed up nearly 950MB of graphics memory for the loss of three to five frames per second. On a card with 6GB or 8GB, it can be the difference between a game running smoothly and one that runs out of memory.
HAGS was introduced in a May 2020 Windows 10 update. Before then, a high-priority CPU thread coordinated and scheduled all the work that programs sent to the graphics card. With HAGS on, the graphics card handles most of that scheduling itself. While it's on by default on most PCs, it's worth testing game by game on a 6- or 8GB card to see if disabling it frees up VRAM at the cost of a few frames.
Source: Engadget · Summarized by HeadlinesBriefing