Add VMMetric and some sample 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"
+#include "vm/object.h"
+
+namespace dart {
+
+VMMetric* VMMetric::vm_list_head_ = NULL;
+
+VMMetric::VMMetric()
+    : isolate_(NULL),
+      name_(NULL),
+      description_(NULL),
+      unit_(kCounter),
+      value_(0),
+      next_(NULL) {
+}
+
+
+void VMMetric::Init(Isolate* isolate,
+                    const char* name,
+                    const char* description,
+                    Unit unit) {

[koda, 2014/08/13 22:42:59]

Assert Init is called only once.

[Cutch, 2014/08/14 20:56:19]

Done.

+  isolate_ = isolate;
+  name_ = name;
+  description_ = description;
+  unit_ = unit;
+  RegisterWithIsolate();
+}
+
+
+void VMMetric::Init(const char* name, const char* description, Unit unit) {
+  name_ = name;
+  description_ = description;
+  unit_ = unit;
+  RegisterWithVM();
+}
+
+
+VMMetric::~VMMetric() {
+  if (isolate_ == NULL) {
+    DeregisterWithVM();
+  } else {
+    DeregisterWithIsolate();
+  }
+}
+
+
+static const char* UnitString(intptr_t unit) {
+  switch (unit) {
+    case VMMetric::kCounter: return "counter";

[koda, 2014/08/13 22:42:59]

I suppose this mapping will need to be sync'ed with a corresponding one in the
Observatory. If so, then the header might be a more suitable place for it, but
I'll leave it up to you.

[Cutch, 2014/08/14 20:56:19]

Acknowledged.

+    case VMMetric::kByte: return "byte";
+    default:
+      UNREACHABLE();
+  }
+  UNREACHABLE();
+  return NULL;
+}
+
+
+void VMMetric::PrintJSON(JSONStream* stream) {
+  JSONObject obj(stream);
+  obj.AddProperty("type", "Counter");
+  obj.AddProperty("name", name_);
+  obj.AddProperty("description", description_);
+  obj.AddProperty("unit", UnitString(unit()));
+  obj.AddPropertyF("id", "metrics/vm/%s", name_);

[koda, 2014/08/13 22:42:59]

There is nothing that distinguishes per-isolate metrics from vm-global metrics.
Consider including an isolate reference on the per-isolate ones.

[Cutch, 2014/08/14 20:56:18]

It is distinguished in libservice by the Metric's "owner" field. We usually
don't send references to owner of objects.

+  // TODO(johnmccutchan): Overflow?
+  double value_as_double = static_cast<double>(Value());
+  obj.AddProperty("value", value_as_double);
+}
+
+
+void VMMetric::RegisterWithIsolate() {

[koda, 2014/08/13 22:42:59]

Assert no duplicate registration?

[Cutch, 2014/08/14 20:56:19]

Done.

+  ASSERT(isolate_ != NULL);
+  ASSERT(next_ == NULL);
+  VMMetric* head = isolate_->metrics_list_head();
+  if (head != NULL) {
+    set_next(head);
+  }
+  isolate_->set_metrics_list_head(this);
+}
+
+
+void VMMetric::DeregisterWithIsolate() {
+  VMMetric* head = isolate_->metrics_list_head();
+  ASSERT(head != NULL);
+  // Handle head of list case.
+  if (head == this) {
+    isolate_->set_metrics_list_head(next());
+    set_next(NULL);
+    return;
+  }
+  VMMetric* previous = NULL;
+  while (true) {
+    previous = head;
+    ASSERT(previous != NULL);
+    head = head->next();
+    if (head == NULL) {
+      break;
+    }
+    if (head == this) {
+      // Remove this from list.
+      previous->set_next(head->next());
+      set_next(NULL);
+      return;
+    }
+    ASSERT(head != NULL);
+  }
+  UNREACHABLE();
+}
+
+
+void VMMetric::RegisterWithVM() {

[koda, 2014/08/13 22:42:59]

Ditto.

[Cutch, 2014/08/14 20:56:18]

Done.

+  ASSERT(isolate_ == NULL);
+  ASSERT(next_ == NULL);
+  VMMetric* head = vm_list_head_;
+  if (head != NULL) {
+    set_next(head);
+  }
+  vm_list_head_ = this;
+}
+
+
+void VMMetric::DeregisterWithVM() {
+  ASSERT(isolate_ == NULL);
+  VMMetric* head = vm_list_head_;
+  if (head == NULL) {
+    return;
+  }
+  // Handle head of list case.
+  if (head == this) {
+    vm_list_head_ = next();
+    set_next(NULL);
+    return;
+  }
+  VMMetric* previous = NULL;
+  while (true) {
+    previous = head;
+    ASSERT(previous != NULL);
+    head = head->next();
+    if (head == NULL) {
+      break;
+    }
+    if (head == this) {
+      // Remove this from list.
+      previous->set_next(head->next());

[koda, 2014/08/13 22:42:59]

Just a general observation: we have lots of linked list implementations in the
VM; "someone" should make a utility like GrowableArray...

[Cutch, 2014/08/14 20:56:18]

Acknowledged.

+      set_next(NULL);
+      return;
+    }
+    ASSERT(head != NULL);
+  }
+  UNREACHABLE();
+}
+
+
+int64_t VMMetricHeapOldUsed::Value() const {
+  Isolate* isolate = Isolate::Current();

[koda, 2014/08/13 22:42:59]

Shouldn't these all use "isolate_" rather than the current isolate?

[Cutch, 2014/08/14 20:56:18]

Done and also ASSERT(isolate() == Isolate::Current());

+  return isolate->heap()->UsedInWords(Heap::kOld) * kWordSize;
+}
+
+
+int64_t VMMetricHeapOldCapacity::Value() const {
+  Isolate* isolate = Isolate::Current();
+  return isolate->heap()->CapacityInWords(Heap::kOld) * kWordSize;
+}
+
+
+int64_t VMMetricHeapOldExternal::Value() const {
+  Isolate* isolate = Isolate::Current();
+  return isolate->heap()->ExternalInWords(Heap::kOld) * kWordSize;
+}
+
+
+int64_t VMMetricHeapNewUsed::Value() const {
+  Isolate* isolate = Isolate::Current();
+  return isolate->heap()->UsedInWords(Heap::kNew) * kWordSize;
+}
+
+
+int64_t VMMetricHeapNewCapacity::Value() const {
+  Isolate* isolate = Isolate::Current();
+  return isolate->heap()->CapacityInWords(Heap::kNew) * kWordSize;
+}
+
+
+int64_t VMMetricHeapNewExternal::Value() const {
+  Isolate* isolate = Isolate::Current();
+  return isolate->heap()->ExternalInWords(Heap::kNew) * kWordSize;
+}
+
+
+int64_t VMMetricIsolateCount::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
+
+
+void VMMetric::InitOnce() {
+#define VM_METRIC_INIT(type, variable, name, unit)                             \
+  vm_metric_##variable##_.Init(name, NULL, VMMetric::unit);
+  VM_METRIC_LIST(VM_METRIC_INIT);
+#undef VM_METRIC_INIT
+}
+
+}  // namespace dart