Add MemoryCoordinatorImpl

content/browser/memory/memory_coordinator_impl.cc

Index: content/browser/memory/memory_coordinator_impl.cc
diff --git a/content/browser/memory/memory_coordinator_impl.cc b/content/browser/memory/memory_coordinator_impl.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d7051c2b94adea17835e946835d495973209ab5d
--- /dev/null
+++ b/content/browser/memory/memory_coordinator_impl.cc
@@ -0,0 +1,191 @@
+// Copyright 2016 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 "content/browser/memory/memory_coordinator_impl.h"
+
+#include "base/threading/thread_task_runner_handle.h"
+#include "content/browser/memory/memory_monitor.h"
+#include "content/public/common/content_features.h"
+
+namespace content {
+
+namespace {
+
+// A expected renderer size. These values come from the median of appropriate
+// UMA stats.
+#if defined(OS_ANDROID) || defined(OS_IOS)
+const int kDefaultExpectedRendererSizeMB = 40;
+#elif defined(OS_WIN)
+const int kDefaultExpectedRendererSizeMB = 70;
+#else // Mac, Linux, and ChromeOS
+const int kDefaultExpectedRendererSizeMB = 120;
+#endif
+
+// Default values for parameters to determine the global state.
+const int kDefaultNewRenderersUntilThrottled = 4;
+const int kDefaultNewRenderersUntilSuspended = 2;
+const int kDefaultNewRenderersBackToNormal = 5;
+const int kDefaultNewRenderersBackToThrottled = 3;
+const int kDefaultMinimumTransitionPeriodSeconds = 30;
+const int kDefaultMonitoringIntervalSeconds = 5;
+
+mojom::MemoryState ToMojomMemoryState(base::MemoryState state) {
+  switch (state) {
+    case base::MemoryState::UNKNOWN:
+      return mojom::MemoryState::UNKNOWN;
+    case base::MemoryState::NORMAL:
+      return mojom::MemoryState::NORMAL;
+    case base::MemoryState::THROTTLED:
+      return mojom::MemoryState::THROTTLED;
+    case base::MemoryState::SUSPENDED:
+      return mojom::MemoryState::SUSPENDED;
+    default:
+      NOTREACHED();
+      return mojom::MemoryState::UNKNOWN;
+  }
+}
+
+}  // namespace
+
+// SingletonTraits for MemoryCoordinator. Returns MemoryCoordinatorImpl
+// as an actual instance.
+struct MemoryCoordinatorSingletonTraits
+    : public base::LeakySingletonTraits<MemoryCoordinator> {
+  static MemoryCoordinator* New() {
+    return new MemoryCoordinatorImpl(base::ThreadTaskRunnerHandle::Get(),
+                                     CreateMemoryMonitor());
+  }
+};
+
+// static
+MemoryCoordinator* MemoryCoordinator::GetInstance() {
+  if (!base::FeatureList::IsEnabled(features::kMemoryCoordinator))
+    return nullptr;
+  return base::Singleton<MemoryCoordinator,
+                         MemoryCoordinatorSingletonTraits>::get();
+}
+
+MemoryCoordinatorImpl::MemoryCoordinatorImpl(
+    scoped_refptr<base::SingleThreadTaskRunner> task_runner,
+    std::unique_ptr<MemoryMonitor> memory_monitor)
+    : task_runner_(task_runner),
+      memory_monitor_(std::move(memory_monitor)),
+      weak_ptr_factory_(this) {
+  DCHECK(memory_monitor_.get());
+  update_state_callback_ = base::Bind(&MemoryCoordinatorImpl::UpdateState,
+                                      weak_ptr_factory_.GetWeakPtr());
+
+  // Set initial parameters for calculating the global state.
+  expected_renderer_size_ = kDefaultExpectedRendererSizeMB;
+  new_renderers_until_throttled_ = kDefaultNewRenderersUntilThrottled;
+  new_renderers_until_suspended_ = kDefaultNewRenderersUntilSuspended;
+  new_renderers_back_to_normal_ = kDefaultNewRenderersBackToNormal;
+  new_renderers_back_to_throttled_ = kDefaultNewRenderersBackToThrottled;
+  minimum_transition_period_ =
+      base::TimeDelta::FromSeconds(kDefaultMinimumTransitionPeriodSeconds);
+  monitoring_interval_ =
+      base::TimeDelta::FromSeconds(kDefaultMonitoringIntervalSeconds);
+}
+
+MemoryCoordinatorImpl::~MemoryCoordinatorImpl() {}
+
+void MemoryCoordinatorImpl::Start() {
+  DCHECK(CalledOnValidThread());
+  DCHECK(last_state_change_.is_null());
+  DCHECK(ValidateParameters());
+  ScheduleUpdateState(base::TimeDelta());
+}
+
+void MemoryCoordinatorImpl::OnChildAdded(int render_process_id) {
+  // Populate the global state as an initial state of a newly created process.
+  SetMemoryState(render_process_id, ToMojomMemoryState(current_state_));
+}
+
+base::MemoryState MemoryCoordinatorImpl::CalculateNextState() {
+  using MemoryState = base::MemoryState;
+
+  int available = memory_monitor_->GetFreeMemoryUntilCriticalMB();
+  if (available <= 0)
+    return MemoryState::SUSPENDED;
+
+  int expected_renderer_count = available / expected_renderer_size_;
+
+  switch (current_state_) {
+    case MemoryState::NORMAL:
+      if (expected_renderer_count <= new_renderers_until_suspended_)
+        return MemoryState::SUSPENDED;
+      if (expected_renderer_count <= new_renderers_until_throttled_)
+        return MemoryState::THROTTLED;
+      return MemoryState::NORMAL;
+    case MemoryState::THROTTLED:
+      if (expected_renderer_count <= new_renderers_until_suspended_)
+        return MemoryState::SUSPENDED;
+      if (expected_renderer_count >= new_renderers_back_to_normal_)
+        return MemoryState::NORMAL;
+      return MemoryState::THROTTLED;
+    case MemoryState::SUSPENDED:
+      if (expected_renderer_count >= new_renderers_back_to_normal_)
+        return MemoryState::NORMAL;
+      if (expected_renderer_count >= new_renderers_back_to_throttled_)
+        return MemoryState::THROTTLED;
+      return MemoryState::SUSPENDED;
+    case MemoryState::UNKNOWN:
+      // Fall through
+    default:
+      NOTREACHED();
+      return MemoryState::UNKNOWN;
+  }
+}
+
+void MemoryCoordinatorImpl::UpdateState() {
+  base::TimeTicks now = base::TimeTicks::Now();
+  MemoryState prev_state = current_state_;
+  MemoryState next_state = CalculateNextState();
+
+  if (last_state_change_.is_null() || current_state_ != next_state) {
+    current_state_ = next_state;
+    last_state_change_ = now;
+  }
+
+  if (next_state != prev_state) {
+    NotifyStateToClients();
+    NotifyStateToChildren();
+    ScheduleUpdateState(minimum_transition_period_);
+  } else {
+    ScheduleUpdateState(monitoring_interval_);
+  }
+}
+
+void MemoryCoordinatorImpl::NotifyStateToClients() {
+  // SUSPENDED state may not make sense to the browser process. Use THROTTLED
+  // instead when the global state is SUSPENDED.
+  // TODO(bashi): Maybe worth considering another state for the browser.
+  auto state = current_state_ == MemoryState::SUSPENDED ? MemoryState::THROTTLED
+                                                        : current_state_;
+  base::MemoryCoordinatorClientRegistry::GetInstance()->Notify(state);
+}
+
+void MemoryCoordinatorImpl::NotifyStateToChildren() {
+  auto mojo_state = ToMojomMemoryState(current_state_);
+  // It's OK to call SetMemoryState() unconditionally because it checks whether
+  // this state transition is valid.
+  // TODO(bashi): In SUSPENDED state, we should update children's state
+  // accordingly when the foreground tab is changed (e.g. resume a renderer
+  // which becomes foreground and suspend a renderer which goes to background).
+  for (auto& iter : children())
+    SetMemoryState(iter.first, mojo_state);
+}
+
+void MemoryCoordinatorImpl::ScheduleUpdateState(base::TimeDelta delta) {
+  task_runner_->PostDelayedTask(FROM_HERE, update_state_callback_, delta);
+}
+
+bool MemoryCoordinatorImpl::ValidateParameters() {
+  return (new_renderers_until_throttled_ > new_renderers_until_suspended_) &&
+      (new_renderers_back_to_normal_ > new_renderers_back_to_throttled_) &&
+      (new_renderers_back_to_normal_ > new_renderers_until_throttled_) &&
+      (new_renderers_back_to_throttled_ > new_renderers_until_suspended_);
+}
+
+}  // namespace content