java - What GC parameters is a JVM running with?

Question

I'm still investigating issues I have with GC tuning (see prior question), which involves lots of reading and experimentation.

Sun Java5+ JVMs attempt to automatically select the optimal GC strategy and parameters based on their environment, which is great, but I can't figure out how to query the running JVM to find out what those parameters are.

Ideally, I'd like to see what values of the various GC-related -XX options are being used, as selected automatically by the VM. If I had that, I could have a baseline to begin tweaking.

Anyone know to recover these values from a running VM?

Answer 1

-XX:+PrintCommandLineFlags Prints flags passed on command line or configured by the ergonomics (auto-sizing) features.

-XX:+PrintFlagsInitial Dumps ALL the default flags and values.

-XX:+PrintFlagsFinal Dumps ALL the flags after processing command line and ergonomics.

So I think the latter will do for you, just add it to your command line script.