A rewritten version of the garbage collection tracing tool for Java programs, Elephant Tracks, developed by the RedLine Research Group @ Tufts University Department of Computer Science.

ET2 is written from scratch in order to improve the performance of Elephant Tracks and for compatibility with the HotSpot JVM. Instead of using the ASM library for instrumentation (and forking Java processes to do so) and relying on the JNI to write instrumentation methods, ET2 uses the native instrumentation library JNIF and write all instrumentation methods in Java.

Moreover, instead of creating and tracing object graphs at runtime as the current implementation of Elephant Tracks does, ET2 generates data that allows the object graphs to be generated post-mortem.

The short-term performance goal is a 1/3 performance boost compared to the current implementation of Elephant Tracks. In the long term, we aspire to increase the performance of Elephant Tracks by 7-10 times.

java -agentlib:et2 [Class], all other Java options (including -jar) work as usual.

• gcc
• JNIF, available from here.
• Oracle JDK 8 or IBM J9 JDK.
• Linux. Only tested with RHEL and Ubuntu; not tested with other distributions or operating systems.

• Ensure JAVA_HOME is set correctly
• Set the variables in Makefile.inc
• make

• make test
• java -agentlib:et2 Test

ET2/JVM runs correctly and without thrown exceptions on the Oracle and IBM J9 JDKs, but throws a ClassCircularityError on OpenJDK. This exception is not yet known to cause any runtime errors, but it is probably a better idea to use Oracle JDK instead of OpenJDK (since both run the HotSpot JVM anyway).