Jetty/Howto/Garbage Collection

Introduction

Tuning the garbage collection (GC) of the JVM can greatly improve Jetty performance. Specifically, you can avoid pauses while the system performs full garbage collections. Optimal tuning of the GC depends on the behaviour of the application and requires detailed analysis, however there are general recommendations.

Examples

These options are general to the Sun JVM, and work in a JDK 6 installation. They provide good information about how your JVM is running; based on that initial information, you can then tune more finely.

To print the implicit flags with which the JVM is configured:

   -XX:+PrintCommandLineFlags 

To disable explicit GC performed regularly by RMI:

   -XX:+DisableExplicitGC 

To print the date and time stamps of GC activity with details:

   -XX:+PrintGCDateStamps \
   -XX:+PrintGCTimeStamps \
   -XX:+PrintGCDetails \
   -XX:+PrintTenuringDistribution

To log GC details to a file:

   -Xloggc:[path/to/gc.log] 

To print GC activity with less detail:

   -verbose:gc 

To use the concurrent marksweep GC with full GC at 80% old generation full:

   -XX:+UseConcMarkSweepGC \
   -XX:CMSInitiatingOccupancyFraction=80