Add max post-gc heap usage metrics

runtime/vm/metrics.cc

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/metrics.h"
 
 #include "vm/isolate.h"
 #include "vm/json_stream.h"
 #include "vm/native_entry.h"
 #include "vm/runtime_entry.h"
@@ skipping 258 matching lines @@
   return isolate()->heap()->CapacityInWords(Heap::kNew) * kWordSize;
 }
 
 
 int64_t MetricHeapNewExternal::Value() const {
   ASSERT(isolate() == Isolate::Current());
   return isolate()->heap()->ExternalInWords(Heap::kNew) * kWordSize;
 }
 
 
+int64_t MetricHeapUsed::Value() const {
+  ASSERT(isolate() == Isolate::Current());
+  return isolate()->heap()->UsedInWords(Heap::kNew) * kWordSize +
+         isolate()->heap()->UsedInWords(Heap::kOld) * kWordSize;

[koda, 2015/10/06 18:09:02]

May overflow.

[koda, 2015/10/06 18:24:03]

Actually, we should simply change the return type of all the public methods
{Heap,PageSpace,Scavenger}::*InWords to int64_t, since none of them should be
hot.

[Cutch, 2015/10/06 20:23:18]

Done.

+}
+
 int64_t MetricIsolateCount::Value() const {
   return Isolate::IsolateListLength();
 }
 
 #define VM_METRIC_VARIABLE(type, variable, name, unit)                         \
   static type vm_metric_##variable##_;
   VM_METRIC_LIST(VM_METRIC_VARIABLE);
 #undef VM_METRIC_VARIABLE
 
 
@@ skipping 38 matching lines @@
 }
 
 
 void MinMetric::SetValue(int64_t new_value) {
   if (new_value < value()) {
     set_value(new_value);
   }
 }
 
 }  // namespace dart