Add --print-metrics vm flag for printing metrics to console

runtime/vm/metrics.cc

Index: runtime/vm/metrics.cc
diff --git a/runtime/vm/metrics.cc b/runtime/vm/metrics.cc
index 0e04e6bc1df648db2633d81013fa65279d824ea3..79038fb1f266f2588919773c14920df0d8401fc1 100644
--- a/runtime/vm/metrics.cc
+++ b/runtime/vm/metrics.cc
@@ -9,9 +9,13 @@
 #include "vm/native_entry.h"
 #include "vm/runtime_entry.h"
 #include "vm/object.h"
+#include "vm/log.h"
 
 namespace dart {
 
+DEFINE_FLAG(bool, print_metrics, false,
+            "Print metrics when isolates (and the VM) are shutdown.");
+
 Metric* Metric::vm_list_head_ = NULL;
 
 Metric::Metric()
@@ -92,6 +96,48 @@ void Metric::PrintJSON(JSONStream* stream) {
 }
 
 
+char* Metric::ValueToString(int64_t value, Unit unit) {
+  Thread* thread = Thread::Current();
+  ASSERT(thread != NULL);
+  Zone* zone = thread->zone();
+  ASSERT(zone != NULL);
+  switch (unit) {
+    case kCounter:
+      return zone->PrintToString("%" Pd64 "", value);
+    case kByte: {
+      const char* scaled_suffix = "b";
+      double scaled_value = static_cast<double>(value);
+      if (value > KB) {
+        scaled_suffix = "kb";
+        scaled_value /= KB;
+      } else if (value > MB) {
+        scaled_suffix = "mb";
+        scaled_value /= MB;
+      } else if (value > GB) {
+        scaled_suffix = "gb";
+        scaled_value /= GB;
+      }
+      return zone->PrintToString("%.3f %s (%" Pd64 ")",
+                                 scaled_value,
+                                 scaled_suffix,
+                                 value);
+    }
+    default:
+      UNREACHABLE();
+      return NULL;
+  }
+}
+
+
+char* Metric::ToString() {
+  Thread* thread = Thread::Current();
+  ASSERT(thread != NULL);
+  Zone* zone = thread->zone();
+  ASSERT(zone != NULL);
+  return zone->PrintToString("%s %s", name(), ValueToString(value(), unit()));
+}
+
+
 bool Metric::NameExists(Metric* head, const char* name) {
   ASSERT(name != NULL);
   while (head != NULL) {
@@ -247,4 +293,18 @@ void Metric::InitOnce() {
 #undef VM_METRIC_INIT
 }
 
+void Metric::Cleanup() {
+  if (FLAG_print_metrics) {
+    // Create a zone to allocate temporary strings in.
+    StackZone sz(Thread::Current());
+    OS::Print("Printing metrics for VM\n");
+    Metric* current = Metric::vm_head();
+    while (current != NULL) {
+      OS::Print("%s\n", current->ToString());
+      current = current->next();
+    }
+    OS::Print("\n");
+  }
+}
+
 }  // namespace dart