We noticed that test/micro/org/openjdk/bench/vm/compiler/WriteBarrier.java
has a System.gc() at the end of its setup method, which will cause the test have only old-to-old refs. We could improve this benchmark by also testing old-to-young refs, it could be done, for example, by adding a per iteration setup to reallocate some of the buffers and not do a System.gc().