I encountered severe performance problems when using the customized warnings parser plugin with regex. It takes about a minute to parse the 250kb file in the attachment for warnings. Even a simple regex like just "INFO" takes 40 sec for the attached file.
A 6 MB log file took about 18 minutes with a slightly more difficult script. When I tested a log on java with about the same size and similar amount of categories, it terminated after 2 seconds.