src/hotspot/share/gc/shenandoah/shenandoahRootProcessor.hpp

rev 59533 : 8246097: Shenandoah: limit parallelism in CLDG root handling
Reviewed-by: XXX

@@ -224,13 +224,22 @@
 };
 
 template <bool CONCURRENT, bool SINGLE_THREADED>
 class ShenandoahClassLoaderDataRoots {
 private:
+  ShenandoahSharedSemaphore     _semaphore;
   ShenandoahPhaseTimings::Phase _phase;
+
+  static uint worker_count(uint n_workers) {
+    // Limit concurrency a bit, otherwise it wastes resources when workers are tripping
+    // over each other. This also leaves free workers to process other parts of the root
+    // set, while admitted workers are busy with doing the CLDG walk.
+    return MAX2(1u, MIN2(ShenandoahSharedSemaphore::max_tokens(), n_workers / 2));
+  }
+
 public:
-  ShenandoahClassLoaderDataRoots(ShenandoahPhaseTimings::Phase phase);
+  ShenandoahClassLoaderDataRoots(ShenandoahPhaseTimings::Phase phase, uint n_workers);
   ~ShenandoahClassLoaderDataRoots();
 
   void always_strong_cld_do(CLDClosure* clds, uint worker_id);
   void cld_do(CLDClosure* clds, uint worker_id);
 };