The latest stable GeoServer version, 1.7.5, was released with a small but critical bug that slows down rendering when a very small polygon or a line is displayed at a high zoom level (so that the displayed area is a very small fraction of the whole). The slowdown increases as one zooms in, and eventually may lead the Java Virtual Machine to crash. The bug also makes for non optimal rendering of cased roads (the typical highway display).
The issue is actually due to a Sun Java bug, but happily we have a workaround for it. If you find you’re affected by this problem, follow these simple instructions:
download this patch jar and save it under geoserver/WEB-INF/lib
Voilà, bug gone.
We want to thank Stefan Ziegler for the quick bug report and the other users that reminded us of how important this patch is.