CPPcheck might be taking over 3,823,295ms loading a 500-job project on account of, possibly, one erroneous file. Or something. Long story short, I used the JavaMelody monitoring in Jenkins and saw that cppCheckResult was taking a HELL of a long time with one method call, and other attempts to find other ways to do this or ways around the bug have given, at best, nothing.
Handling GET /job/-------/cppcheckResult/graph : RequestHandlerThread24
3 823 295 0 0 com.thoughtworks.xstream.converters.reflection.FieldDictionary.fieldOrNull(FieldDictionary.java:113)
It's a "replicatable" problem on our servers, but since it's internal stuff I can't link you to it.