nt # Enter a description of the change.

runtime/vm/code_generator.cc

Index: runtime/vm/code_generator.cc
diff --git a/runtime/vm/code_generator.cc b/runtime/vm/code_generator.cc
index 41175a72f4e4da6ec19ea601d977ff216b75549a..4ab89ca6e7260fe4025b94ac6fff64b7ad9b8468 100644
--- a/runtime/vm/code_generator.cc
+++ b/runtime/vm/code_generator.cc
@@ -1448,10 +1448,12 @@ DEFINE_RUNTIME_ENTRY(OptimizeInvokedFunction, 1) {
   ASSERT(function.HasCode());
 
   if (CanOptimizeFunction(function, isolate)) {
-    // Reset usage counter for reoptimization before calling optimizer to
-    // prevent recursive triggering of function optimization.
-    function.set_usage_counter(0);
     if (FLAG_background_compilation) {
+      // Reduce the chance of triggering optimization while the function is
+      // being optimized in the background. INT_MIN should ensure that it takes
+      // long time to trigger optimization.
+      // Note that the background compilation queue rejects duplicate entries.
+      function.set_usage_counter(INT_MIN);
       BackgroundCompiler::EnsureInit(thread);
       ASSERT(isolate->background_compiler() != NULL);
       isolate->background_compiler()->CompileOptimized(function);
@@ -1459,6 +1461,10 @@ DEFINE_RUNTIME_ENTRY(OptimizeInvokedFunction, 1) {
       arguments.SetReturn(Code::Handle(zone, function.CurrentCode()));
       return;
     }
+
+    // Reset usage counter for reoptimization before calling optimizer to
+    // prevent recursive triggering of function optimization.
+    function.set_usage_counter(0);
     if (FLAG_trace_compiler) {
       if (function.HasOptimizedCode()) {
         THR_Print("ReCompiling function: '%s' \n",