Description Bill Joy 2008-12-04 10:43:48 EST

Multiple Java reconciler threads running can lead to UI hang and sometimes thread crashes due to "too many open files" I/O errors.

This is on build M20080911-1700, OS=win32, ARCH=x86, WS=win32, NL=en_US.

I used the "Import Existing Projects into Workspace" wizard and imported one plugin project. My workspace already had over 30 related plugin projects in the workspace. I also had several Java files open (I think that is probably a key point). Build automatically was also enabled.

There was a really long wait with the progress dialog up (I invoked an action which was blocked until the rebuild was complete). I took a thread dump in the console window (I started Eclipse with eclipsec.exe) and saw many  "org.eclipse.jdt.internal.ui.text.JavaReconciler" threads running. My guess is that there was one of these per file that I had open. All these threads were doing zip file operations called by the method JarPackageFragmentRoot.computeChildren().

Suddenly there was exception after exception about "too many open files".

I think part of the problem is related to JavaModelManager which appears to now cache zip file handles on a thread basis. Having multiple reconciler threads running at the same time when there are many JAR files on the classpath of each project would therefore seem dangerous when Windows only has a limited file handle pool.

There are also some major performance implications here that I don't understand.

Guessing from the Error Log entries, there is probably some synchronization between the threads happening since the threads are complaining about the same archive in consecutive entries. Perhaps contention between the threads is part of the performance problem.