RFR (round 1), JDK-8214259: Implementation: JEP 189: Shenandoah: A Low-Pause Garbage Collector

[Kim Barrett]

A few quick comments (not a real review).

> On Nov 26, 2018, at 4:39 PM, Roman Kennke <rkennke at redhat.com> wrote:
> 
> Sections to review (at this point) are the following:
> 
>  *) shared-gc
>     - This is mostly boilerplate that is common to any GC
>     - referenceProcessor.cpp has a little change to make one assert not fail (next to CMS and G1)

Ick.  But I don’t have a better suggestion that doesn’t involve adding a new API
to CollectedHeap for use by this assertion, which seems a bit excessive if there
are no other uses.

>     - taskqueue.hpp has some small adjustments to enable subclassing

Why this change instead of JDK-8204947?  As the description from that RFE says:
"The ShenandoahTaskTerminator from the Shenandoah project is a much better implementation of a task terminator.”