Accessing shared data requires dereferencing a pointer?

[arthur.avramiea]

Page 156 of the book, section 5.5.3 says Private Versus Shared Data it says: Accessing shared data also requires dereferencing a pointer, which incurs a performance overhead.
What I have understood until now is that each thread gets a local copy of the shared data, and it can update the value of the other threads using flush.
In this context, can you help me understand which is the pointer that the book is talking about there?

[ejd]

Each thread doesn't get a local copy of the shared data. Each thread accesses the shared data, usually through a pointer, and the shared data may be copied into a thread's cache when used. Hope that helps explain the problem you are having with the concept.