8349915: CTW: Lots of level 3 compiles are done at level 2 after JDK-8348570

Reviewed-by: kvn, chagedorn

Author: shipilev

src/hotspot/share/compiler/compilationPolicy.cpp

@@ -633,6 +633,11 @@ CompileTask* CompilationPolicy::select_task(CompileQueue* compile_queue) {
       task = next_task;
       continue;
     }
+    if (task->compile_reason() == CompileTask::Reason_Whitebox) {
+      // Whitebox (CTW) tasks do not participate in rate selection and/or any level
+      // adjustments. Just return them in order.
+      return task;
+    }
     Method* method = task->method();
     methodHandle mh(Thread::current(), method);
     if (task->can_become_stale() && is_stale(t, TieredCompileTaskTimeout, mh) && !is_old(mh)) {

src/hotspot/share/compiler/compileTask.hpp

@@ -199,6 +199,8 @@ class CompileTask : public CHeapObj<mtCompiler> {
   int          comp_level()                      { return _comp_level;}
   void         set_comp_level(int comp_level)    { _comp_level = comp_level;}
 
+  CompileReason compile_reason()                 { return _compile_reason; }
+
   AbstractCompiler* compiler() const;
   CompileTask*      select_for_compilation();