Tips and Tricks

Tips and Tricks

Sometimes running WALA for quick and accurate results takes some finesse. These tips and tricks should help.

Performance Tips

Heap Size

Use -Xmx<n>M to set the heap size to n megabytes. Use -verbose:gc to see if it looks like the VM is in the GC region of discontent.

Want to get an idea where memory is going? Check out the HeapTracer utility. It's slow, but I find it useful.

Libraries

Many analyses (e.g. call graph construction) may run dramatically faster when analyzing earlier versions (e.g. 1.4) of the JDK, since 5.0+ libraries introduce various sorts of pollution that we haven't tracked down yet. You may want to prototype your analysis against a 1.4 JDK, and then move up to a later version, perhaps using an Exclusions file later to recover lost performance.

Exclusions File

WALA supports an XML-based exclusions file, which tells WALA to ignore certain classes or packages. Using an exclusions file can drastically speed up analysis, although of course introduces potential unsoundness.

For example, you can use the following code (from CallGraphTestUtil) to build an analysis scope that excludes classes based on an exclusions file.

public static AnalysisScope makeJ2SEAnalysisScope(String scopeFile, String exclusionsFile) {
  AnalysisScope scope = AnalysisScopeReader.read(scopeFile, exclusionsFile, MY_CLASSLOADER);
  return scope;
}

For a client that uses this, see the CallGraphTest.testPrimordial() unit test.

Here are the contents of GUIExclusions.txt, an exclusions file which tells WALA to ignore AWT-related classes. When using these exclusions, WALA pretends that classes from java.awt don't exist.

java\/awt\/.*
javax\/swing\/.*
sun\/awt\/.*
sun\/swing\/.*

Other Issues

Something seem too slow? Let us know how to reproduce the problem. Maybe we'll fix it.