RFR: Passive heuristics should consistently process refs and unload classes

[Aleksey Shipilev]

We have copied the random block from Aggressive policy to Passive one. The goal
for random selection in Aggressive is to exercise all paths. For Passive, we are
better off being consistent:

$ hg diff
diff -r 1d44a55dc2c9 src/share/vm/gc/shenandoah/shenandoahCollectorPolicy.cpp
--- a/src/share/vm/gc/shenandoah/shenandoahCollectorPolicy.cpp	Tue May 30
09:45:47 2017 +0200
+++ b/src/share/vm/gc/shenandoah/shenandoahCollectorPolicy.cpp	Tue May 30
09:56:58 2017 +0200
@@ -431,14 +431,14 @@
   }

   virtual bool process_references() {
-    // Randomly process refs with 50% chance.
-    return (os::random() & 1) == 1;
+    // Always process references.
+    return true;
   }

   virtual bool unload_classes() {
     if (ShenandoahUnloadClassesFrequency == 0) return false;
-    // Randomly unload classes with 50% chance.
-    return (os::random() & 1) == 1;
+    // Always unload classes.
+    return true;
   }
 };


Testing: hotspot_gc_shenandoah

Thanks,
-Aleksey