Cleanup allocation site pretenuring tracing, added new flag --trace-pretenuring-statistics.

src/objects-inl.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1532 matching lines @@
 inline void AllocationSite::IncrementMementoCreateCount() {
   ASSERT(FLAG_allocation_site_pretenuring);
   int value = memento_create_count();
   set_memento_create_count(value + 1);
 }
 
 
 inline bool AllocationSite::DigestPretenuringFeedback() {
   bool decision_changed = false;
   int create_count = memento_create_count();
+  int found_count = memento_found_count();
+  double ratio = static_cast<double>(found_count) / create_count;
+  PretenureFlag current_mode = GetPretenureMode();

[mvstanton, 2014/02/06 10:30:42]

This is a little more expensive, because we are only computing ratio for
printing purposes if we didn't meet kPretenureMinimumCreated.

Can it be organized such that we don't compute ratio if there is no audience for
the computation?

[Hannes Payer (out of office), 2014/02/06 10:47:27]

I do not think that this is an issue, but we can do that.

+
   if (create_count >= kPretenureMinimumCreated) {
-    int found_count = memento_found_count();
-    double ratio = static_cast<double>(found_count) / create_count;
-    if (FLAG_trace_track_allocation_sites) {
-      PrintF("AllocationSite: %p (created, found, ratio) (%d, %d, %f)\n",
-             static_cast<void*>(this), create_count, found_count, ratio);
-    }
-    int current_mode = GetPretenureMode();
     PretenureDecision result = ratio >= kPretenureRatio
         ? kTenure
         : kDontTenure;
     set_pretenure_decision(result);
     if (current_mode != GetPretenureMode()) {
       decision_changed = true;
       dependent_code()->MarkCodeForDeoptimization(
           GetIsolate(),
           DependentCode::kAllocationSiteTenuringChangedGroup);
     }
   }
 
+  if (FLAG_trace_pretenuring_statistics) {
+    PrintF(
+        "AllocationSite(%p): (created, found, ratio) (%d, %d, %f) %s => %s\n",
+         static_cast<void*>(this), create_count, found_count, ratio,
+         current_mode == TENURED ? "tenured" : "not tenured",
+         GetPretenureMode() == TENURED ? "tenured" : "not tenured");
+  }
+

[mvstanton, 2014/02/06 10:30:42]

Why drive a VW when you can have a Cadillac? Can the printing tell us about the
decision making above, like: did we decide, or did we "change our mind" and mark
for deopt?

[Hannes Payer (out of office), 2014/02/06 10:47:27]

We do exactly that in old state => new state.

   // Clear feedback calculation fields until the next gc.
   set_memento_found_count(0);
   set_memento_create_count(0);
   return decision_changed;
 }
 
 
 void JSObject::EnsureCanContainHeapObjectElements(Handle<JSObject> object) {
   object->ValidateElements();
   ElementsKind elements_kind = object->map()->elements_kind();
@@ skipping 5199 matching lines @@
 #undef READ_UINT32_FIELD
 #undef WRITE_UINT32_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_