Drop the global memory state from memory coordinator

content/browser/memory/memory_coordinator_impl.cc

 // 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/memory/memory_coordinator_client_registry.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/process/process_handle.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/trace_event/trace_event.h"
+#include "content/browser/memory/memory_condition_observer.h"
 #include "content/browser/memory/memory_monitor.h"
-#include "content/browser/memory/memory_state_updater.h"
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_types.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/render_widget_host.h"
 #include "content/public/common/content_features.h"
 #include "mojo/public/cpp/bindings/binding.h"
 
 namespace content {
 
 namespace {
 
+const int kDefaultMinimumTransitionPeriodSeconds = 30;
+
 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;
   }
 }
 
+const char* MemoryConditionToString(MemoryCondition condition) {
+  switch (condition) {
+    case MemoryCondition::NORMAL:
+      return "normal";
+    case MemoryCondition::WARNING:
+      return "warning";
+    case MemoryCondition::CRITICAL:
+      return "critical";
+  }
+  NOTREACHED();
+  return "N/A";
+}
+
 }  // namespace
 
 // The implementation of MemoryCoordinatorHandle. See memory_coordinator.mojom
 // for the role of this class.
 class MemoryCoordinatorHandleImpl : public mojom::MemoryCoordinatorHandle {
  public:
   MemoryCoordinatorHandleImpl(mojom::MemoryCoordinatorHandleRequest request,
                               MemoryCoordinatorImpl* coordinator,
                               int render_process_id);
   ~MemoryCoordinatorHandleImpl() override;
@@ skipping 53 matching lines @@
     return nullptr;
   return base::Singleton<MemoryCoordinatorImpl,
                          MemoryCoordinatorImplSingletonTraits>::get();
 }
 
 MemoryCoordinatorImpl::MemoryCoordinatorImpl(
     scoped_refptr<base::SingleThreadTaskRunner> task_runner,
     std::unique_ptr<MemoryMonitor> memory_monitor)
     : delegate_(GetContentClient()->browser()->GetMemoryCoordinatorDelegate()),
       memory_monitor_(std::move(memory_monitor)),
-      state_updater_(base::MakeUnique<MemoryStateUpdater>(this, task_runner)) {
+      condition_observer_(
+          base::MakeUnique<MemoryConditionObserver>(this, task_runner)),
+      minimum_state_transition_period_(base::TimeDelta::FromSeconds(
+          kDefaultMinimumTransitionPeriodSeconds)) {
   DCHECK(memory_monitor_.get());
   base::MemoryCoordinatorProxy::SetMemoryCoordinator(this);
 }
 
 MemoryCoordinatorImpl::~MemoryCoordinatorImpl() {}
 
 void MemoryCoordinatorImpl::Start() {
   DCHECK(CalledOnValidThread());
   DCHECK(last_state_change_.is_null());
 
   notification_registrar_.Add(
       this, NOTIFICATION_RENDER_WIDGET_VISIBILITY_CHANGED,
       NotificationService::AllBrowserContextsAndSources());
-  last_state_change_ = base::TimeTicks::Now();
-  state_updater_->ScheduleUpdateState(base::TimeDelta());
+  condition_observer_->ScheduleUpdateCondition(base::TimeDelta());
 }
 
 void MemoryCoordinatorImpl::CreateHandle(
     int render_process_id,
     mojom::MemoryCoordinatorHandleRequest request) {
   std::unique_ptr<MemoryCoordinatorHandleImpl> handle(
       new MemoryCoordinatorHandleImpl(std::move(request), this,
                                       render_process_id));
   handle->binding().set_connection_error_handler(
       base::Bind(&MemoryCoordinatorImpl::OnConnectionError,
                  base::Unretained(this), render_process_id));
   CreateChildInfoMapEntry(render_process_id, std::move(handle));
 }
 
 bool MemoryCoordinatorImpl::SetChildMemoryState(int render_process_id,
                                                 MemoryState memory_state) {
   // Can't set an invalid memory state.
   if (memory_state == MemoryState::UNKNOWN)
     return false;
 
   // Can't send a message to a child that doesn't exist.
   auto iter = children_.find(render_process_id);
   if (iter == children_.end())
     return false;
 
   // Can't send a message to a child that isn't bound.
   if (!iter->second.handle->child().is_bound())
     return false;
 
-  memory_state = OverrideGlobalState(memory_state, iter->second);
+  memory_state = OverrideState(memory_state, iter->second);
 
   // A nop doesn't need to be sent, but is considered successful.
   if (iter->second.memory_state == memory_state)
     return true;
 
   // Can't suspend the given renderer.
   if (memory_state == MemoryState::SUSPENDED &&
       !CanSuspendRenderer(render_process_id))
     return false;
 
   // Update the internal state and send the message.
   iter->second.memory_state = memory_state;
   iter->second.handle->child()->OnStateChange(ToMojomMemoryState(memory_state));
   return true;
 }
 
 base::MemoryState MemoryCoordinatorImpl::GetChildMemoryState(
     int render_process_id) const {
   auto iter = children_.find(render_process_id);
   if (iter == children_.end())
     return base::MemoryState::UNKNOWN;
   return iter->second.memory_state;
 }
 
 void MemoryCoordinatorImpl::RecordMemoryPressure(
     base::MemoryPressureMonitor::MemoryPressureLevel level) {
   // TODO(bashi): Record memory pressure level.
 }
 
-base::MemoryState MemoryCoordinatorImpl::GetGlobalMemoryState() const {
-  return current_state_;
+base::MemoryState MemoryCoordinatorImpl::GetBrowserMemoryState() const {
+  return browser_memory_state_;
 }
 
 base::MemoryState MemoryCoordinatorImpl::GetCurrentMemoryState() const {
-  // 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.
-  return current_state_ == MemoryState::SUSPENDED ? MemoryState::THROTTLED
-                                                  : current_state_;
+  return GetBrowserMemoryState();
 }
 
 void MemoryCoordinatorImpl::SetCurrentMemoryStateForTesting(
     base::MemoryState memory_state) {
-  // This changes the current state temporariy for testing. The state will be
-  // updated 1 minute later.
-  ForceSetGlobalState(memory_state, base::TimeDelta::FromMinutes(1));
+  // Resets |last_state_change_| so that NotifyStateToBrowser() to set
+  // memory state forcibly.
+  last_state_change_ = base::TimeTicks();
+  NotifyStateToBrowser(memory_state);
 }
 
-void MemoryCoordinatorImpl::ForceSetGlobalState(base::MemoryState new_state,
-                                                base::TimeDelta duration) {
-  DCHECK(new_state != MemoryState::UNKNOWN);
-  ChangeStateIfNeeded(current_state_, new_state);
-  state_updater_->ScheduleUpdateState(duration);
+void MemoryCoordinatorImpl::ForceSetMemoryCondition(MemoryCondition condition,
+                                                    base::TimeDelta duration) {
+  UpdateConditionIfNeeded(condition);
+  condition_observer_->ScheduleUpdateCondition(duration);
 }
 
 void MemoryCoordinatorImpl::Observe(int type,
                                     const NotificationSource& source,
                                     const NotificationDetails& details) {
   DCHECK(type == NOTIFICATION_RENDER_WIDGET_VISIBILITY_CHANGED);
   RenderWidgetHost* render_widget_host = Source<RenderWidgetHost>(source).ptr();
   RenderProcessHost* process = render_widget_host->GetProcess();
   if (!process)
     return;
   auto iter = children().find(process->GetID());
   if (iter == children().end())
     return;
+
   iter->second.is_visible = *Details<bool>(details).ptr();
-  auto new_state = GetGlobalMemoryState();
+  // The current heuristics for state calculation:
+  // - Foregrounded renderers: THROTTLED when condition is CRITICAL, otherwise
+  //   NORMAL.
+  // - Backgrounded renderers: THROTTLED when condition is WARNING/CRITICAL,
+  //   otherwise NORMAL.
+  MemoryState new_state = MemoryState::NORMAL;
+  MemoryCondition condition = GetMemoryCondition();
+  if (condition == MemoryCondition::WARNING) {
+    new_state =
+        iter->second.is_visible ? MemoryState::NORMAL : MemoryState::THROTTLED;
+  } else if (condition == MemoryCondition::CRITICAL) {
+    new_state = MemoryState::THROTTLED;
+  }
   SetChildMemoryState(iter->first, new_state);
 }
 
 base::MemoryState MemoryCoordinatorImpl::GetStateForProcess(
     base::ProcessHandle handle) {
   DCHECK(CalledOnValidThread());
   if (handle == base::kNullProcessHandle)
     return MemoryState::UNKNOWN;
   if (handle == base::GetCurrentProcessHandle())
-    return GetCurrentMemoryState();
+    return browser_memory_state_;
 
   for (auto& iter : children()) {
     auto* render_process_host = GetRenderProcessHost(iter.first);
     if (render_process_host && render_process_host->GetHandle() == handle)
       return iter.second.memory_state;
   }
   return MemoryState::UNKNOWN;
 }
 
-bool MemoryCoordinatorImpl::ChangeStateIfNeeded(base::MemoryState prev_state,
-                                                base::MemoryState next_state) {
+void MemoryCoordinatorImpl::UpdateConditionIfNeeded(
+    MemoryCondition next_condition) {
   DCHECK(CalledOnValidThread());
-  if (prev_state == next_state)
-    return false;
+  if (memory_condition_ == next_condition)
+    return;
 
-  last_state_change_ = base::TimeTicks::Now();
-  current_state_ = next_state;
+  MemoryCondition prev_condition = memory_condition_;
+  memory_condition_ = next_condition;
 
   TRACE_EVENT2(TRACE_DISABLED_BY_DEFAULT("memory-infra"),
-               "MemoryCoordinatorImpl::ChangeStateIfNeeded", "prev",
-               MemoryStateToString(prev_state), "next",
-               MemoryStateToString(next_state));
-  NotifyStateToClients();
-  NotifyStateToChildren();
-  return true;
+               "MemoryCoordinatorImpl::UpdateConditionIfNeeded", "prev",
+               MemoryConditionToString(prev_condition), "next",
+               MemoryConditionToString(next_condition));
+
+  // TODO(bashi): Following actions are tentative. We might want to prioritize
+  // processes and handle them one-by-one.
+
+  if (next_condition == MemoryCondition::NORMAL) {
+    // Set NORMAL state to all clients/processes.
+    NotifyStateToBrowser(MemoryState::NORMAL);
+    NotifyStateToChildren(MemoryState::NORMAL);
+  } else if (next_condition == MemoryCondition::WARNING) {
+    // Set NORMAL state to foreground proceses and clients in the browser
+    // process. Set THROTTLED state to background processes.
+    NotifyStateToBrowser(MemoryState::NORMAL);
+    for (auto& iter : children()) {
+      auto state =
+          iter.second.is_visible ? MemoryState::NORMAL : MemoryState::THROTTLED;
+      SetChildMemoryState(iter.first, state);
+    }
+    // Idea: Purge memory from background processes.
+  } else if (next_condition == MemoryCondition::CRITICAL) {
+    // Set THROTTLED state to all clients/processes.
+    NotifyStateToBrowser(MemoryState::THROTTLED);
+    NotifyStateToChildren(MemoryState::THROTTLED);
+    // Idea: Start discarding tabs.
+  }
 }
 
 void MemoryCoordinatorImpl::DiscardTab() {
   if (delegate_)
     delegate_->DiscardTab();
 }
 
 RenderProcessHost* MemoryCoordinatorImpl::GetRenderProcessHost(
     int render_process_id) {
   return RenderProcessHost::FromID(render_process_id);
@@ skipping 26 matching lines @@
     return false;
   if (render_process_host->GetWorkerRefCount() > 0)
     return false;
   // Assumes that we can't suspend renderers if there is no delegate.
   if (!delegate_)
     return false;
   return delegate_->CanSuspendBackgroundedRenderer(render_process_id);
 }
 
 void MemoryCoordinatorImpl::OnChildAdded(int render_process_id) {
-  // Populate the global state as an initial state of a newly created process.
-  auto new_state = GetGlobalMemoryState();
+  // Populate an initial state of a newly created process, assuming it's
+  // foregrounded.

[haraken, 2017/03/03 02:08:00]

You don't need to fix this in this CL but this assumption may not be correct.
e.g., a case where users restore many tabs at the same time.

Either way, it looks better to share the following code with
MemoryCoordinatorImpl::Observe.

[bashi, 2017/03/03 02:41:32]

Agreed. Added TODO.

+  auto new_state = GetMemoryCondition() == MemoryCondition::CRITICAL
+                       ? MemoryState::THROTTLED
+                       : MemoryState::NORMAL;
   SetChildMemoryState(render_process_id, new_state);
 }
 
-base::MemoryState MemoryCoordinatorImpl::OverrideGlobalState(
-    MemoryState memory_state,
-    const ChildInfo& child) {
+base::MemoryState MemoryCoordinatorImpl::OverrideState(MemoryState memory_state,
+                                                       const ChildInfo& child) {
   // We don't suspend foreground renderers. Throttle them instead.
   if (child.is_visible && memory_state == MemoryState::SUSPENDED)
     return MemoryState::THROTTLED;
 #if defined(OS_ANDROID)
   // On Android, we throttle background renderers immediately.
   // TODO(bashi): Create a specialized class of MemoryCoordinator for Android
   // and move this ifdef to the class.
   if (!child.is_visible && memory_state == MemoryState::NORMAL)
     return MemoryState::THROTTLED;
   // TODO(bashi): Suspend background renderers after a certain period of time.
 #endif  // defined(OS_ANDROID)
   return memory_state;
 }
 
 void MemoryCoordinatorImpl::CreateChildInfoMapEntry(
     int render_process_id,
     std::unique_ptr<MemoryCoordinatorHandleImpl> handle) {
   auto& child_info = children_[render_process_id];
   // Process always start with normal memory state.
   // We'll set renderer's memory state to the current global state when the
   // corresponding renderer process is ready to communicate. Renderer processes
   // call AddChild() when they are ready.
   child_info.memory_state = MemoryState::NORMAL;
   child_info.is_visible = true;
   child_info.handle = std::move(handle);
 }
 
-void MemoryCoordinatorImpl::NotifyStateToClients() {
-  auto state = GetCurrentMemoryState();
+void MemoryCoordinatorImpl::NotifyStateToBrowser(
+    base::MemoryState memory_state) {
+  if (memory_state == browser_memory_state_)

[bashi, 2017/03/02 08:59:31]

unittests catched the bug. I should have added this line.

+    return;
+
+  base::TimeTicks now = base::TimeTicks::Now();
+  if (!last_state_change_.is_null() &&
+      (now - last_state_change_ < minimum_state_transition_period_))
+    return;
+
+  last_state_change_ = now;
+  browser_memory_state_ = memory_state;
+  NotifyStateToClients(memory_state);
+}
+
+void MemoryCoordinatorImpl::NotifyStateToClients(MemoryState state) {
   base::MemoryCoordinatorClientRegistry::GetInstance()->Notify(state);
 }
 
-void MemoryCoordinatorImpl::NotifyStateToChildren() {
+void MemoryCoordinatorImpl::NotifyStateToChildren(MemoryState state) {
   // It's OK to call SetChildMemoryState() unconditionally because it checks
   // whether this state transition is valid.
   for (auto& iter : children())
-    SetChildMemoryState(iter.first, current_state_);
+    SetChildMemoryState(iter.first, state);
 }
 
 MemoryCoordinatorImpl::ChildInfo::ChildInfo() {}
 
 MemoryCoordinatorImpl::ChildInfo::ChildInfo(const ChildInfo& rhs) {
   // This is a nop, but exists for compatibility with STL containers.
 }
 
 MemoryCoordinatorImpl::ChildInfo::~ChildInfo() {}
 
 }  // namespace content