NOCOMMIT PROTOTYPE [GRC] Tab CPU Usage Observer

services/resource_coordinator/coordination_unit/tab_cpu_usage_observer.cc

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "services/resource_coordinator/coordination_unit/tab_cpu_usage_observer.h"
+
+#include <stdint.h>
+
+#include <ostream>
+#include <utility>
+
+#include "base/values.h"
+#include "services/resource_coordinator/coordination_unit/coordination_unit_impl.h"
+#include "services/resource_coordinator/public/cpp/coordination_unit_id.h"
+#include "services/resource_coordinator/public/interfaces/coordination_unit.mojom.h"
+
+namespace resource_coordinator {
+
+const unsigned int TabObserver::kMaxCPUUsageMeasurementTicks = 3;
+
+TabObserver::TabObserver() : cpu_measurement_ticks_(0u) {}
+
+TabObserver::~TabObserver() = default;
+
+void TabObserver::AttributeCPUUsage(double cpu_usage) {
+  ++cpu_measurement_ticks_;
+}
+
+bool TabObserver::IsObserving() {
+  return !url_.empty() && cpu_measurement_ticks_ < kMaxCPUUsageMeasurementTicks;
+}
+
+void TabObserver::TabURLChanged(
+    const CoordinationUnitImpl* tab_coordination_unit,
+    mojom::PropertyType tab_url_property) {
+  DCHECK(tab_coordination_unit->id().type ==
+         CoordinationUnitType::kWebContents);
+  DCHECK(tab_url_property == mojom::PropertyType::kTabURL);
+
+  base::Value tab_url_value =
+      tab_coordination_unit->GetProperty(tab_url_property);
+  DCHECK(tab_url_value.is_string());
+  url_ = tab_url_value.GetString();
+
+  // Reset ticks
+  cpu_measurement_ticks_ = 0u;
+}
+
+ProcessObserver::ProcessObserver() = default;
+
+ProcessObserver::~ProcessObserver() = default;
+
+void ProcessObserver::RecalculateAttributableTabs(
+    const CoordinationUnitImpl* process_coordination_unit,
+    const CoordinationUnitImpl* frame_coordination_unit) {
+  DCHECK(process_coordination_unit->id().type ==
+         CoordinationUnitType::kProcess);
+  DCHECK(frame_coordination_unit->id().type == CoordinationUnitType::kFrame);
+
+  attributable_tabs_.clear();
+
+  DCHECK(tab_cpu_usage_observer_);
+  std::unordered_map<CoordinationUnitID, TabObserver>&
+      registered_tab_observers = tab_cpu_usage_observer_->tab_observers();
+  // Any WebContents CoordinationUnit that is a parent of any of the
+  // Process's child Frame CoordinationUnit is considered to attributable
+  // for the Process's CPU usage.
+  for (auto* child : process_coordination_unit->children()) {
+    if (child->id().type == CoordinationUnitType::kFrame) {
+      for (auto* frame_parent : child->parents()) {
+        if (frame_parent->id().type == CoordinationUnitType::kWebContents) {
+          // Another frame within a tab may have previously inserted its, so
+          // its acceptable to not check if the insertion was successful.
+          auto tab_observer_it =
+              registered_tab_observers.find(frame_parent->id());
+          DCHECK(tab_observer_it != registered_tab_observers.end());
+          attributable_tabs_.insert(
+              std::make_pair(frame_parent->id(), &tab_observer_it->second));
+        }
+      }
+    }
+  }
+}
+
+void ProcessObserver::NewCPUUsageMeasurement(
+    const CoordinationUnitImpl* process_coordination_unit,
+    mojom::PropertyType process_cpu_usage_property) {
+  DCHECK(process_coordination_unit->id().type ==
+         CoordinationUnitType::kProcess);
+  DCHECK(process_cpu_usage_property == mojom::PropertyType::kProcessCPUUsage);
+
+  if (attributable_tabs_.empty()) {
+    return;
+  }
+
+  base::Value process_cpu_usage_value =
+      process_coordination_unit->GetProperty(process_cpu_usage_property);
+  DCHECK(process_cpu_usage_value.is_double());
+
+  // CPU attribution for multiple tabs within a process is currently naive in
+  // that the measured process CPU utilization is attributed equally amongst the
+  // tabs.
+  double tab_cpu_usage = process_cpu_usage_value.GetDouble() /
+                         static_cast<double>(attributable_tabs_.size());
+
+  for (auto& tab_observer : attributable_tabs_) {
+    if (tab_observer.second->IsObserving()) {
+      tab_observer.second->AttributeCPUUsage(tab_cpu_usage);
+    }
+  }
+}
+
+TabCPUUsageObserver::TabCPUUsageObserver() = default;
+
+TabCPUUsageObserver::~TabCPUUsageObserver() = default;
+
+void TabCPUUsageObserver::TabCoordinationUnitCreated(
+    CoordinationUnitImpl* tab_coordination_unit) {
+  DCHECK(!tab_observers_.count(tab_coordination_unit->id()));
+
+  auto& tab_observer = tab_observers_[tab_coordination_unit->id()];
+  tab_observer.SetTabCPUUsageObserver(this);
+
+  tab_coordination_unit->on_property_changed_event_listeners().AddListener(
+      base::Bind(&TabObserver::TabURLChanged, base::Unretained(&tab_observer)),
+      mojom::PropertyType::kTabURL);
+
+  tab_coordination_unit->on_will_be_destroyed_event_listeners().AddListener(
+      base::Bind(&TabCPUUsageObserver::RemoveTabObserver,
+                 base::Unretained(this)));
+}
+
+void TabCPUUsageObserver::ProcessCoordinationUnitCreated(
+    CoordinationUnitImpl* process_coordination_unit) {
+  DCHECK(!process_observers_.count(process_coordination_unit->id()));
+  ProcessObserver& process_observer =
+      process_observers_[process_coordination_unit->id()];
+  process_observer.SetTabCPUUsageObserver(this);
+
+  process_coordination_unit->on_add_child_event_listeners().AddListener(
+      base::Bind(&ProcessObserver::RecalculateAttributableTabs,
+                 base::Unretained(&process_observer)),
+      CoordinationUnitType::kFrame);
+
+  process_coordination_unit->on_remove_child_event_listeners().AddListener(
+      base::Bind(&ProcessObserver::RecalculateAttributableTabs,
+                 base::Unretained(&process_observer)),
+      CoordinationUnitType::kFrame);
+
+  process_coordination_unit->on_property_changed_event_listeners().AddListener(
+      base::Bind(&ProcessObserver::NewCPUUsageMeasurement,
+                 base::Unretained(&process_observer)),
+      mojom::PropertyType::kProcessCPUUsage);

[Zhen Wang, 2017/06/16 22:47:45]

I see your point here that one may want to listen to multiple property types (or
CU types for other listeners).

But I think you can get this done similarly with the typical observer pattern. I
admit that you need one more switch to dispatch the 2 property types.


void TabCPUUsageObserver::TabCoordinationUnitCreated(tab_coordination_unit) {
  DCHECK(!tab_observers_.count(tab_coordination_unit->id()));
  auto& tab_observer = tab_observers_[tab_coordination_unit->id()];
  tab_observer.SetTabCPUUsageObserver(this);

  cu->ObservePropertyChangeEvent(this, mojom::PropertyType::kTabURL);
  // And other ones...
}

void
TabCPUUsageObserver::ProcessCoordinationUnitCreated(process_coordination_unit) {
  DCHECK(!process_observers_.count(process_coordination_unit->id()));
  ProcessObserver& process_observer =
      process_observers_[process_coordination_unit->id()];
  process_observer.SetTabCPUUsageObserver(this);

  cu->ObservePropertyChangeEvent(this, mojom::PropertyType::kProcessCPUUsage);
  // And other ones...
}

// This is the new API replacing the callback way.
TabCPUUsageObserver::OnPropertyChanged(cu, property) {
  switch (property.type) {
    case mojom::PropertyType::kTabURL:
      GetTabObserver(cu)->TabURLChanged(cu, property);
    case mojom::PropertyType::kProcessCPUUsage:
      GetProcessObserver(cu)->NewCPUUsageMeasurement(cu, property);
    default:
      DCHECK(false); // should never happen
  }
}

TabCPUUsageObserver::GetTabObserver(cu) {
  // can be implemented with a map
}

TabCPUUsageObserver::GetTabObserver(cu) {
  // can be implemented with a map
}

+
+  process_coordination_unit->on_will_be_destroyed_event_listeners().AddListener(
+      base::Bind(&TabCPUUsageObserver::RemoveProcessObserver,
+                 base::Unretained(this)));
+}
+
+void TabCPUUsageObserver::CoordinationUnitCreated(
+    CoordinationUnitImpl* coordination_unit) {
+  switch (coordination_unit->id().type) {
+    case CoordinationUnitType::kWebContents:
+      TabCoordinationUnitCreated(coordination_unit);
+      break;
+    case CoordinationUnitType::kProcess:
+      ProcessCoordinationUnitCreated(coordination_unit);
+      break;
+    case CoordinationUnitType::kFrame:
+      break;
+    default:
+      break;
+  }
+
+  if (coordination_unit->id().type != CoordinationUnitType::kProcess) {
+    return;
+  }
+}
+
+void TabCPUUsageObserver::RemoveProcessObserver(
+    const CoordinationUnitImpl* process_coordination_unit) {
+  DCHECK(process_observers_.count(process_coordination_unit->id()));
+  process_observers_.erase(process_coordination_unit->id());
+}
+
+void TabCPUUsageObserver::RemoveTabObserver(
+    const CoordinationUnitImpl* tab_coordination_unit) {
+  DCHECK(tab_observers_.count(tab_coordination_unit->id()));
+  tab_observers_.erase(tab_coordination_unit->id());
+}
+
+}  // namespace resource_coordinator