RFR: Adjust worker threads according to refproc-ergo decisions

[Roman Kennke]

Last upstream merge brought some ReferenceProcessor goodness, in which
the RP would tell the task executors how many worker threads it
considers useful. This change makes the reference task executors use as
many threads as it's told.

Testing: tier3_gc_shenandoah


# HG changeset patch
# User rkennke
# Date 1529928409 -7200
#      Mon Jun 25 14:06:49 2018 +0200
# Node ID 93432b06f44cf0ecc66a6691e600f9de6cc2e86a
# Parent  1f5c9cf67f8f00e41056b406de986be3115f0f99
Adjust worker threads according to refproc-ergo decisions

diff --git
a/src/hotspot/share/gc/shenandoah/shenandoahConcurrentMark.cpp
b/src/hotspot/share/gc/shenandoah/shenandoahConcurrentMark.cpp
--- a/src/hotspot/share/gc/shenandoah/shenandoahConcurrentMark.cpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahConcurrentMark.cpp
@@ -664,6 +664,9 @@

     ShenandoahHeap* heap = ShenandoahHeap::heap();
     ShenandoahConcurrentMark* cm = heap->concurrentMark();
+    ShenandoahWorkerScope scope(_workers,
+                                ergo_workers,
+                                "reference processing");
     uint nworkers = _workers->active_workers();
     cm->task_queues()->reserve(nworkers);
     if (UseShenandoahOWST) {
diff --git a/src/hotspot/share/gc/shenandoah/shenandoahTraversalGC.cpp
b/src/hotspot/share/gc/shenandoah/shenandoahTraversalGC.cpp
--- a/src/hotspot/share/gc/shenandoah/shenandoahTraversalGC.cpp
+++ b/src/hotspot/share/gc/shenandoah/shenandoahTraversalGC.cpp
@@ -1068,6 +1068,9 @@

     ShenandoahHeap* heap = ShenandoahHeap::heap();
     ShenandoahTraversalGC* traversal_gc = heap->traversal_gc();
+    ShenandoahWorkerScope scope(_workers,
+                                ergo_workers,
+                                "reference processing");
     uint nworkers = _workers->active_workers();
     traversal_gc->task_queues()->reserve(nworkers);
     if (UseShenandoahOWST) {