While working on JDK-8356848, I noticed that Shenandoah doesn't use the API in collectedHeap for printing the heap before/after a GC invocation/cycle. All other GCs (except for Epsilon) use this API, and I think a common API/printing style is a nice to have in this case (GC log tools/analyzers might share logic between GCs for example).

When using "print_before_gc" or "print_after_gc", the print is also logged to an event ring-buffer, which is printed in hs_err files. This section is currently empty when running with Shenandoah, which is another reason I think this is nice to have.

I'm not 100% familiar with Shenandoah logging, so this functionality might already be present, in which case I suggest moving to the common API instead.