Thursday, 26 April 2012

Optimize Netbeans 7.1 Memory and Configuration in OS X Manually

Reducing the memory footprint of Netbeans is often a good idea. Even on a system with plenty of RAM, a typical setup for development can quickly consume all free memory, leading to slowdowns and thrashing due to paging. Additionally, setting the initial memory usage high enough can avoid excessive memory allocations early on during the program's execution.

This post serves as a reminder of how to configure Netbeans and monitor its memory usage. It is not meant to be comprehensive, however I hope it turns out to be helpful for someone nonetheless.


The most direct way to configure memory usage in Netbeans 7.1 is by editing its configuration file. In OS X, the Netbeans configuration file is located directly within the application bundle. In finder, it can be found by the following:

  1. Go to your Applications folder
  2. Go into the Netbeans folder
  3. Secondary-click on the Netbeans 7.1 app, and view package contents
  4. Look for the file Contents/Resources/Netbeans/etc/netbeans.conf
  5. (optional) Backup the original in case you need to undo your changes
  6. Edit the netbeans.conf configuration file

If you would rather use terminal instead, the following string is the file's location (note that this is a single line, and any apparent line breaks are due to the blog format):


Note that this location is OS X specific, and in other platforms the location may vary. See the following site for details:

In this file, flags to configure how the Java virtual machine runs Netbeans can be set. A good overview of these can be found here:

The following is an example of a tweaked configuration for netbeans_default_options:

-J-client -J-Xss2m -J-Xms256m -J-Xmx512m -J-XX:PermSize=32m -J-XX:MaxPermSize=160m -J-Dapple.laf.useScreenMenuBar=true -J-Dsun.java2d.noddraw=true -J-XX:+UseConcMarkSweepGC -J-XX:+CMSClassUnloadingEnabled -J-XX:+CMSPermGenSweepingEnabled


The easiest way to monitor the memory usage of Netbeans is to use the memory toolbar. To do this, in your menu select: View->Toolbars->Memory

In order to force garbage collection to free up some memory, simply click on the memory toolbar.

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