gravitystorm/openstreetmap-carto — pull request #51 by pnorman (2013-05-22 00:56:11+00:00)
Title: Disable polygon clipping for buildings

Buildings tend to be smaller than tiles, meaning its cheaper to render the occasional building outside the meta-tile that matches && than to check all of them.

On my test EC2 setup it increased rendering rate by 3.5% for the benchmarking workload which fit into ram caches.

The increase in speed is dependent on zoom with the greatest time decrease of 2.6%-3.0% from z16-z18, an decrease of 0.6%-1.3% for z13-z15 and insufficient tiles rendered for higher zooms. Note: speed and rate are not inverses of each other due to multi-threading issues.

For the larger benchmarking workload which involved disk accesses it increased rate by 0.5%.