The graphics processing unit described herein is configured to process graphics data using a rendering space which is sub-divided into a plurality of tiles. The graphics processing unit comprises a tiling unit and rendering logic. The tiling unit is arranged to generate a tile control list for each tile, the tile control list identifying each graphics data item present in the tile. The rendering logic is arranged to render the tiles using the tile control lists generated by the tiling unit. The tiling unit comprises per-tile hash generation logic arranged to generate, for each tile, a per-tile hash value based on a set of textures that will be accessed when processing the tile in the rendering logic, and the tiling unit is further arranged to store the per-tile hash value for a tile within the tile control list for the tile.