The point that "we know something the JVM can't know", eg, that this JVM is running a web server, is fair. I'm still not convinced that specifying the CMS collector is the right application of this knowledge, and I'm new to Ubuntu (from a contributor standpoint, anyway) so I don't know what the project goals are for the default configuration. But for now let me move down what I hope is a fruitful path. It sounds like (and please correct me if I'm wrong) we want to choose settings that:
1) at a minimum, "work" (eg, after running apt-get, tomcat actually boots up and serves requests) 2) has reasonable defaults to suit the sort of hardware we expect people to run web servers on Currently our defaults are: -Xmx128M -XX:+UseConcMarkSweepGC Which satisfies #1, but I still think is not great for #2. Maybe as you alluded we'd do better by not specifying the maximum heap size? The rationale was that 64MB is not usually enough, and that made sense under JDK1.4, when this was the default heap size. However it looks like in 1.5 and later, the heap selection was changed to be based on the amount of available RAM *** initial heap size: Larger of 1/64th of the machine's physical memory on the machine or some reasonable minimum. Before J2SE 5.0, the default initial heap size was a reasonable minimum, which varies by platform. You can override this default using the -Xms command-line option. maximum heap size: Smaller of 1/4th of the physical memory or 1GB. Before J2SE 5.0, the default maximum heap size was 64MB. You can override this default using the -Xmx command-line option. *** So if we don't give any heap parameters to the JVM: - The heap will be at least 128MB (satisfy goal #1) on any machine with 512MB or more of RAM - The JVM is free to choose a heap much larger than 128MB, based on the available memory (satisfy goal #2) For this reason I'd suggest we remove the "-Xmx128M" portion from the command line. References: http://java.sun.com/javase/technologies/hotspot/gc/gc_tuning_6.html#par_gc.ergonomics.default_size http://java.sun.com/javase/6/docs/technotes/guides/vm/gc-ergonomics.html http://java.sun.com/docs/hotspot/gc5.0/ergo5.html -- Using incorrect JVM Garbage Collector https://bugs.launchpad.net/bugs/541520 You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to tomcat6 in ubuntu. -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs
