|UI location||Render Settings > Performance Panel|
|Current version download||http://git.blender.org/gitweb/gitweb.cgi/blender-addons.git/blob_plain/HEAD:/render_auto_tile_size.py|
|Links||Bugs & ChangeLog: https://developer.blender.org/T36785|
Install the addon by opening User Preferences, and choosing "Install from file..." in the Addons tab.
Auto Tile Size should be the only item in the list, but if not, simply search for it. Check the checkbox on the right.
NOTE: The most recent documentation and info can be found here: http://gregzaal.github.io/auto-tile-size/
This addon gives you some quick controls to get the best possible tile sizes for the fastest possible Cycles render. Usually it's a good idea to stick to powers of 2 (16, 64, 256...) to get fast renders, however in the case of tile sizes it's even more important to keep the tiles fairly square and of consistent size. Having some tiles smaller than the rest due to the borders of the image makes for longer renders.
So this addon allows you to choose a target size and then automatically calculates the actual tile dimensions to ensure squareness and consistency.
As a rule of thumb, GPUs like bigger tiles (256 x 256 usually) and CPUs like smaller ones (often 32 square), thus the two target values are stored separately in case you switch between them often.
For a detailed explanation of this reasoning, see this page.
At the bottom of the Performance Panel of the render settings are the target tile sizes.
The best tile size will be calculated and the addon will attempt to stick as close to the target as possible.
In a previous version it was necessary to Set the tile size, however it is now done automatically. After enabling the addon, you can probably forget about tile sizes altogether, though some strange resolutions cannot have nice consistent tile sizes and you may wish to set it manually.
If for some reason you want to set the tile size to exactly the target, resulting in perfectly square tiles but probably some rectangular ones on the edges, disable Consistent Tiles