Understanding memory parameters for Eclipse

Question

I just installed Eclipse 4.2 (Juno) on Linux 64 bit. I have looked at several Eclipse.ini threads on Stack Overflow, but I still don't understand the relationship between the different memory parameters.

On one hand, there are parameters that are for the VM and that go under -vmargs (for example, -Xms and -Xmx, -XX), while others (for example, --launcher.XXMaxPermSize) are provided to Eclipse directly.

What is the relationship between these parameters? How would I set them up for a machine with more than 8 GB of memory?

I am aware of the long Stack Overflow question What are the best JVM settings for Eclipse?, but I would like to learn how to adjust these parameters myself.

For reference, after installation, the default parameters that Juno has are:

-startup plugins/org.eclipse.equinox.launcher_1.3.0.v20120522-1813.jar --launcher.library plugins/org.eclipse.equinox.launcher.gtk.linux.x86_1.1.200.v20120522-1813 -product org.eclipse.epp.package.cpp.product --launcher.defaultAction openFile -showsplash org.eclipse.platform --launcher.XXMaxPermSize 256m --launcher.defaultAction openFile -vmargs -Dosgi.requiredJavaVersion=1.5 -Dhelp.lucene.tokenizer=standard -XX:MaxPermSize=256m -Xms40m -Xmx512m 

Answer 1

If you are running Eclipse on an Oracle/Sun JVM, I would disregard --launcher.XXMaxPermSize (I personally remove it) and concentrate on -XX:MaxPermSize, -Xms and -Xmx.

The reason for --launcher.XXMaxPermSize is that some non-Oracle/Sun JVMs would choke on -XX:MaxPermSize. The launcher is programmed to detect the JVM and conditionally supply -XX:MaxPermSize. This of course is defeated by the explicit -XX:MaxPermSize setting in the default eclipse.ini file. That looks like a bug.

I never mess with -Xms setting. I set -Xmx1024m and -XX:MaxPermSize=512m.