IBM contributed -Xshare option to Java (and OpenJDK as well): $ java -X 2>&1 | grep share -Xshare:off do not attempt to use shared class data -Xshare:auto use shared class data if possible (default) -Xshare:on require using shared class data, otherwise fail. More about this: http://www.ibm.com/developerworks/library/j-sharedclasses/?ca=dgr-jw22ClassShareJRE&S_Tact=105AGX59&S_cmp=GRsitejw22 The option can be used to share classes and improve loading times, which can be dramatic. For Windows, classes cache is generated by default. In Fedora, the cache is not created. I recommend to run the following command in the post installation section of the RPM package: java -Xshare:dump It creates about 25 MB file /usr/lib/jvm/java-1.7.0-openjdk-1.7.0.9.x86_64/jre/lib/amd64/server/classes.jsa Using -Xshare user can take advantage of faster loading, it can be measure even on the hello world application (much more on big applications like Eclipse): [lzap@lzapx Download]$ time java -Xshare:on -cp . HelloWorldApp Hello World! real 0m0.051s user 0m0.038s sys 0m0.012s [lzap@lzapx Download]$ time java -Xshare:off -cp . HelloWorldApp Hello World! real 0m0.076s user 0m0.061s sys 0m0.012s By default it should use the class cache if it is found, but this is not working (is this a bug?): [lzap@lzapx Download]$ time java -cp . HelloWorldApp Hello World! real 0m0.072s user 0m0.054s sys 0m0.017s Tested with F16 and F17, selecting rawhide as I expect this is not implemented.
*** This bug has been marked as a duplicate of bug 513605 ***