Re: [wildfly-dev] Call For Help (Testsuite)

I recently help out on a customer case, which came from the Linux side of the house, which had to do with Java when virtualized. The customer produced a test case that was emulating the application where the performance slowdown was occuring. It turned out that they were using ReentrantReadWriteLock for some synchronization. I did some thread dumps of the test case, and looked at the source too, and found out that ReentrantReadWriteLock was using the ...Unsafe.park() native method, which does a futex() system call. That system call has terrible performance when virtualized, compared to using ReentrantLock, which has been changed with JDK 7 to no longer depend on the native code, and does everything in Java, in user space. Performance was so much better, and with some vitualization configuration settings was almost equal to bare metal performance. That's a long story, just to say, if we have intermittent test suite failures only when run virtualized, perhaps we have some Java code that is using native code that calls futex() in the OS. If so, it will perform very poorly compared to bare metal, and could be part of the problem with intermittent test failures, especially if there are any timing issues in the test cases. Just an FYI for something to look out for. Andy ----- Original Message -----