Add VMMetric and some sample metrics

runtime/vm/metrics.h

Index: runtime/vm/metrics.h
diff --git a/runtime/vm/metrics.h b/runtime/vm/metrics.h
new file mode 100644
index 0000000000000000000000000000000000000000..e77f383d88bf89d84af16f294baf98e7bd614acf
--- /dev/null
+++ b/runtime/vm/metrics.h
@@ -0,0 +1,120 @@
+// 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.
+
+#ifndef VM_METRICS_H_
+#define VM_METRICS_H_
+
+#include "vm/allocation.h"
+
+namespace dart {
+
+class Isolate;
+class JSONStream;
+
+// Metrics for each isolate.
+#define ISOLATE_METRIC_LIST(V)                                                 \
+  V(VMMetricHeapOldUsed, HeapOldUsed, "heap.old.used")                         \
+  V(VMMetricHeapOldCapacity, HeapOldCapacity, "heap.old.capacity")             \
+  V(VMMetricHeapOldExternal, HeapOldExternal, "heap.old.external")             \
+  V(VMMetricHeapNewUsed, HeapNewUsed, "heap.new.used")                         \
+  V(VMMetricHeapNewCapacity, HeapNewCapacity, "heap.new.capacity")             \
+  V(VMMetricHeapNewExternal, HeapNewExternal, "heap.new.external")             \
+
+#define VM_METRIC_LIST(V)                                                      \
+  V(VMMetricIsolateCount, IsolateCount, "vm.isolate.count")                    \
+
+class VMMetric {
+ public:
+  VMMetric();
+
+  static void InitOnce();
+
+  // Initialize and register a counter for an isolate.
+  void Init(Isolate* isolate, const char* name, const char* description);
+  // Initialize and register a counter for the VM.
+  void Init(const char* name, const char* description);
+
+  virtual ~VMMetric();
+
+  void PrintJSON(JSONStream* stream);
+
+  // Override to get a callback when value is needed.
+  virtual int64_t Value() const { return value(); }
+
+  int64_t value() const { return value_; }

[koda, 2014/08/12 22:03:03]

It's confusing to have both value() and Value() in the same public interface. It
it guaranteed that the "consumer" will never call value() directly (if so, then
why does it have access to that method)? Should a subclass always call set_value
when Value is called?

[Cutch, 2014/08/13 17:50:59]

Moved Value to behind 'protected:' and added comments.

+  void set_value(int64_t value) { value_ = value; }
+
+  VMMetric* next() const { return next_; }
+  void set_next(VMMetric* next) {
+    next_ = next;
+  }
+
+  const char* name() const { return name_; }
+
+  Isolate* isolate() const { return isolate_; }
+
+  static VMMetric* vm_head() { return vm_list_head_; }
+
+ private:
+  Isolate* isolate_;
+  const char* name_;
+  const char* description_;
+  int64_t value_;

[koda, 2014/08/12 22:03:03]

int64_t? I thought you had decided on double for all metrics?

[Cutch, 2014/08/13 17:50:59]

On the service it is still a double but I think most(all?) VM metrics will be
integral.

+  VMMetric* next_;
+
+  void RegisterWithIsolate();
+  void DeregisterWithIsolate();
+  void RegisterWithVM();
+  void DeregisterWithVM();
+
+  static VMMetric* vm_list_head_;
+  DISALLOW_COPY_AND_ASSIGN(VMMetric);
+};
+
+
+class VMMetricHeapOldUsed : public VMMetric {

[koda, 2014/08/12 22:03:03]

Please try to minimize the amount of code one must add for a trivial counter.
Ideally, I would love to be able to add a single "increment" statement within a
loop and automagically create a counter (as with the existing counters.h)

[Cutch, 2014/08/13 17:50:59]

A trivial isolate owned counter would require the following:

1) Add a line to ISOLATE_METRIC_LIST:

V(VMMetric, CounterName, "counter.name", kCounter)

2a) To increment the counter:

Isolate::Current()->GetCounterNameMetric()->increment();

2b) To set the counter:

Isolate::Current()->GetCounterNameMetric()->set_value(44);

+ public:
+  virtual int64_t Value() const;
+};
+
+
+class VMMetricHeapOldCapacity : public VMMetric {
+ public:
+  virtual int64_t Value() const;
+};
+
+
+class VMMetricHeapOldExternal : public VMMetric {
+ public:
+  virtual int64_t Value() const;
+};
+
+
+class VMMetricHeapNewUsed : public VMMetric {
+ public:
+  virtual int64_t Value() const;
+};
+
+
+class VMMetricHeapNewCapacity : public VMMetric {
+ public:
+  virtual int64_t Value() const;
+};
+
+
+class VMMetricHeapNewExternal : public VMMetric {
+ public:
+  virtual int64_t Value() const;
+};
+
+
+class VMMetricIsolateCount : public VMMetric {
+ public:
+  virtual int64_t Value() const;
+};
+
+
+}  // namespace dart
+
+#endif  // VM_METRICS_H_