Factor out a Histogram class from HistogramTimer, and use it to measure external fragmentation

src/heap.cc

Index: src/heap.cc
diff --git a/src/heap.cc b/src/heap.cc
index a448292789ad72511cb6c6922dc903bc1f14eb8a..8cf1af84f11ebc3656690bce58e1aec27f6d37c4 100644
--- a/src/heap.cc
+++ b/src/heap.cc
@@ -445,54 +445,26 @@ void Heap::GarbageCollectionEpilogue() {
   isolate_->counters()->number_of_symbols()->Set(
       symbol_table()->NumberOfElements());
 
-  isolate_->counters()->new_space_bytes_available()->Set(
-      static_cast<int>(new_space()->Available()));
-  isolate_->counters()->new_space_bytes_committed()->Set(
-      static_cast<int>(new_space()->CommittedMemory()));
-  isolate_->counters()->new_space_bytes_used()->Set(
-      static_cast<int>(new_space()->SizeOfObjects()));
-
-  isolate_->counters()->old_pointer_space_bytes_available()->Set(
-      static_cast<int>(old_pointer_space()->Available()));
-  isolate_->counters()->old_pointer_space_bytes_committed()->Set(
-      static_cast<int>(old_pointer_space()->CommittedMemory()));
-  isolate_->counters()->old_pointer_space_bytes_used()->Set(
-      static_cast<int>(old_pointer_space()->SizeOfObjects()));
-
-  isolate_->counters()->old_data_space_bytes_available()->Set(
-      static_cast<int>(old_data_space()->Available()));
-  isolate_->counters()->old_data_space_bytes_committed()->Set(
-      static_cast<int>(old_data_space()->CommittedMemory()));
-  isolate_->counters()->old_data_space_bytes_used()->Set(
-      static_cast<int>(old_data_space()->SizeOfObjects()));
-
-  isolate_->counters()->code_space_bytes_available()->Set(
-      static_cast<int>(code_space()->Available()));
-  isolate_->counters()->code_space_bytes_committed()->Set(
-      static_cast<int>(code_space()->CommittedMemory()));
-  isolate_->counters()->code_space_bytes_used()->Set(
-      static_cast<int>(code_space()->SizeOfObjects()));
-
-  isolate_->counters()->map_space_bytes_available()->Set(
-      static_cast<int>(map_space()->Available()));
-  isolate_->counters()->map_space_bytes_committed()->Set(
-      static_cast<int>(map_space()->CommittedMemory()));
-  isolate_->counters()->map_space_bytes_used()->Set(
-      static_cast<int>(map_space()->SizeOfObjects()));
-
-  isolate_->counters()->cell_space_bytes_available()->Set(
-      static_cast<int>(cell_space()->Available()));
-  isolate_->counters()->cell_space_bytes_committed()->Set(
-      static_cast<int>(cell_space()->CommittedMemory()));
-  isolate_->counters()->cell_space_bytes_used()->Set(
-      static_cast<int>(cell_space()->SizeOfObjects()));
-
-  isolate_->counters()->lo_space_bytes_available()->Set(
-      static_cast<int>(lo_space()->Available()));
-  isolate_->counters()->lo_space_bytes_committed()->Set(
-      static_cast<int>(lo_space()->CommittedMemory()));
-  isolate_->counters()->lo_space_bytes_used()->Set(
-      static_cast<int>(lo_space()->SizeOfObjects()));
+#define UPDATE_COUNTERS_FOR_SPACE(space)                                     \
+  isolate_->counters()->space##_bytes_available()->Set(                      \
+      static_cast<int>(space()->Available()));                               \
+  isolate_->counters()->space##_bytes_committed()->Set(                      \
+      static_cast<int>(space()->CommittedMemory()));                         \
+  isolate_->counters()->space##_bytes_used()->Set(                           \
+      static_cast<int>(space()->SizeOfObjects()));                           \
+  if (space()->CommittedMemory() > 0) {                                      \
+    isolate_->counters()->external_fragmentation_##space()->AddSample(       \
+        static_cast<int>(                                                    \
+            (space()->SizeOfObjects() * 100) / space()->CommittedMemory())); \
+  }
+  UPDATE_COUNTERS_FOR_SPACE(new_space)
+  UPDATE_COUNTERS_FOR_SPACE(old_pointer_space)
+  UPDATE_COUNTERS_FOR_SPACE(old_data_space)
+  UPDATE_COUNTERS_FOR_SPACE(code_space)
+  UPDATE_COUNTERS_FOR_SPACE(map_space)
+  UPDATE_COUNTERS_FOR_SPACE(cell_space)
+  UPDATE_COUNTERS_FOR_SPACE(lo_space)
+#undef UPDATE_COUNTERS_FOR_SPACE
 
 #if defined(DEBUG)
   ReportStatisticsAfterGC();