Advanced Setup

This page contains information to help you configure Eclipse and Scala IDE, to increase performances and ease-of-use.

Eclipse Configuration

The default Eclipse heap configuration is often inadequate for the Scala IDE. It is strongly recommended to edit the eclipse/eclipse.ini (eclipse/ on Mac osX) file and add the following lines to increase various heap limits and virtual machine options:


One recent Oracle JVM, the following might also be beneficial:


As is the following on Oracle 64-bits JVM:


Required Preferences

  • JDT Weaving

    Scala IDE uses AOP to tweak the Eclipse JDT, so JDT weaving has to be enable. Otherwise, Scala files would be managed as Java files.

    It is set in the JDT Weaving section of Scala Setup Diagnostics dialog [2]. JDT Weaving should be checked (and disabled, to prevent accidental changes). If it is not the case, click to enable it.


Optional Preferences

  • Heap Status

    When the memory usage nears the limit, the Garbage Collector activity increases (when the compiler runs, ...) and system slows down. It is good to keep a eye on the heap status. It is possible by enabling Show heap status in the General section [1].

  • Limit Simultaneously Open Editors

    Having too many editors open can claim a lot of memory. Unless you are an exceptional multi-tasker or you use a task-focused interface such as Mylyn, you may want to limit the number of simultaneously opened editors in the General section [1].

  • Deactivate Automatic Java Content Assist

    Since Scala-IDE is built over JDT, the Java Content Assist is enabled by default for Scala files, even though it is not relevant for Scala language files development. You can safely deactivate it if most of your edition is done in Scala files.


Naturally, if you have a mixed Scala/Java project, this may not be a good idea : proceed at your own risk.

  • Activate Completion

    You should enable completion however — and you may even want to activate word proposals, if you don’t want to have to hit several shortcuts to complete what you type.



Garbage Collection activity and swap can be really bad for performance. It can trigger Eclipse freezes and cuase a general system slow down.

Monitoring what is happening is the best option to keep a healthy system:

  • to monitor CPU and swap, use your native system monitor (some of the other system monitors are big resource users themselves).
  • to monitor Garbage Collector activity, use visualvm on the eclipse instance. It is a profiling tool provided with jdk 1.6.x. It is possible also to get a feel of the memory usage with the heap status bar Optional Preferences in Eclipse.

Depending of the problem, the memory allocated to the JVM can be increased, or some of the other application closed (like the web browser, or some flash application, ...).

Suggested interesting keyboard shortcuts

You may want to head out to our Suggested Shortcuts page to get a list of shortcuts that will speed up your Scala development.