Why reading a volatile and writing to a field member is not scalable in Java?

Question

Observe the following program written in Java (complete runnable version follows, but the important part of the program is in the snippet a little bit further below):

Answer 1

Short: apparently, the answer is false sharing due to card marking for the GC.

A more extensive explanations is given in this question:

Array allocation and access on the Java Virtual Machine and memory contention