diff -r bf9fa29bb3dc -r bf8128faace1 src/hotspot/share/gc/shenandoah/shenandoahStringDedup.cpp
--- a/src/hotspot/share/gc/shenandoah/shenandoahStringDedup.cpp	Mon Jul 22 10:26:21 2019 -0700
+++ b/src/hotspot/share/gc/shenandoah/shenandoahStringDedup.cpp	Sat Jul 13 12:15:17 2019 -0400
@@ -75,16 +75,20 @@
   assert(SafepointSynchronize::is_at_safepoint(), "Must be at a safepoint");
   assert(is_enabled(), "String deduplication not enabled");
 
-  ShenandoahWorkerTimings* worker_times = ShenandoahHeap::heap()->phase_timings()->worker_times();
-
   StringDedupUnlinkOrOopsDoClosure sd_cl(is_alive, cl);
+  if (ShenandoahGCPhase::is_root_work_phase()) {
+    ShenandoahWorkerTimings* worker_times = ShenandoahHeap::heap()->phase_timings()->worker_times();
+    {
+      ShenandoahWorkerTimingsTracker x(worker_times, ShenandoahPhaseTimings::StringDedupQueueRoots, worker_id);
+      StringDedupQueue::unlink_or_oops_do(&sd_cl);
+    }
 
-  {
-    ShenandoahWorkerTimingsTracker x(worker_times, ShenandoahPhaseTimings::StringDedupQueueRoots, worker_id);
+    {
+      ShenandoahWorkerTimingsTracker x(worker_times, ShenandoahPhaseTimings::StringDedupTableRoots, worker_id);
+      StringDedupTable::unlink_or_oops_do(&sd_cl, worker_id);
+    }
+  } else {
     StringDedupQueue::unlink_or_oops_do(&sd_cl);
-  }
-  {
-    ShenandoahWorkerTimingsTracker x(worker_times, ShenandoahPhaseTimings::StringDedupTableRoots, worker_id);
     StringDedupTable::unlink_or_oops_do(&sd_cl, worker_id);
   }
 }