RFR: Improve/more detailed timing stats for Traversal GC

[Aleksey Shipilev]

On 02/02/2018 03:05 PM, Roman Kennke wrote:
> We've two problems in the timing stats in Traversal GC:
> - the update-roots pass uses final_traversal_gc_work and thus overrides the previous final-traversal
> roots timings.
> - finishing the queues is done in the same pass as root scanning, by the same workers.
> 
> This patch introduces a new set of worker timings for traversal-update-roots and a new worker timing
> item 'Finish Queues'.
> 
> http://cr.openjdk.java.net/~rkennke/traversal-stats/webrev.00/

*) Indent is wrong:

 371   _phase_names[final_update_refs_finish_queues]   = "    UR: Finish Queues";

*) You have _heap field available for this:

  ShenandoahWorkerTimings *worker_times = ShenandoahHeap::heap()->phase_timings()->worker_times();

Otherwise looks good.

Thanks,
-Aleksey