Tile buffers in a graphics processing system are managed use "copy-on-write"
semantics, in which tile data stored in a memory location is not transferred to
another location until the tile data for one of the buffers is modified. Two memory
spaces store tile data, and two logical buffers are used to access the memory spaces.
For each tile, a tile association is maintained, indicating which of the two memory
spaces is associated with each of the two logical buffers. To copy a tile of the
first logical buffer to the second logical buffer, the tile association for the
tile being copied is modified. Data for a tile is written to the memory space associated
with a target logical buffer after ensuring that the tile association for the tile
associates the target logical buffer with a different one of the two memory spaces
from the other logical buffer.
