RFR: Add support for CollectedHeap::get_safepoint_workers()

[Aleksey Shipilev]

On 05/08/2018 05:42 PM, Ramki Ramakrishna wrote:
> Hi Per,
> 
> is there a bug id that you can link to the webrev for background (for those
> who came in late)?

This is the part of what we did in Shenandoah to exploit parallelism during safepoint cleanups:
  https://bugs.openjdk.java.net/browse/JDK-8180932

You'll probably get better results if you can reuse GC worker threads to do the safepoint cleanups,
but that requires GC workers to be suspendable for non-GC safepoints. Having a separate thread pool
is fine for now: Shenandoah does the separate thread pool, the proposed ZGC code also does it.

-Aleksey