Cycles Persistent Data memory limits during animation renders

Scene Data Retention

The Persistent Data feature in Blender's Cycles engine is designed to keep scene data in GPU memory between frames to eliminate the synchronization overhead typically required at the start of each frame in an animation.

Memory Constraints

While this reduces render start times, the retention of geometry and texture data consumes a constant portion of VRAM. In complex scenes, this leaves less available memory for the actual rendering process, potentially triggering out-of-core rendering where the engine swaps data to system RAM.

There is uncertainty regarding the threshold at which the overhead of Persistent Data outweighs the performance gains by forcing the render into a slower out-of-core state.

• How does Cycles prioritize VRAM allocation between Persistent Data and the active render tiles?
• Is there a documented mechanism to limit the amount of memory Persistent Data can reserve?