memory coordinator: Throttle background renderers on Android

content/browser/memory/memory_coordinator.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.h"
 
 #include "base/memory/memory_coordinator_client_registry.h"
 #include "base/metrics/histogram_macros.h"
 #include "content/public/browser/content_browser_client.h"
 #include "content/public/browser/render_process_host.h"
@@ skipping 70 matching lines @@
 
   // 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;
 
-  // We don't suspend foreground renderers. Throttle them instead.
-  if (memory_state == mojom::MemoryState::SUSPENDED &&
-      iter->second.is_visible)
-    memory_state = mojom::MemoryState::THROTTLED;
+  memory_state = OverrideChildState(memory_state, iter->second);

[haraken, 2016/12/09 03:48:50]

OverrideGlobalState ?

I might want to unify terms into "global states" and "local states".

[bashi, 2016/12/09 04:18:45]

Done. Maybe "Override" isn't a good verb for this method. There will be better
name for this method but I couldn't come up with better names.
We can replace "the current state" with "local state" but we still need to say
"child states".

 
   // 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 == mojom::MemoryState::SUSPENDED &&
       !CanSuspendRenderer(render_process_id))
     return false;
 
@@ skipping 61 matching lines @@
 bool MemoryCoordinator::CanSuspendRenderer(int render_process_id) {
   // If there is no delegate (i.e. unittests), renderers are always suspendable.
   if (!delegate_)
     return true;
   auto* render_process_host = RenderProcessHost::FromID(render_process_id);
   if (!render_process_host || !render_process_host->IsProcessBackgrounded())
     return false;
   return delegate_->CanSuspendBackgroundedRenderer(render_process_id);
 }
 
+mojom::MemoryState MemoryCoordinator::OverrideChildState(
+    mojom::MemoryState memory_state,
+    const ChildInfo& child) {
+  // We don't suspend foreground renderers. Throttle them instead.
+  if (child.is_visible && memory_state == mojom::MemoryState::SUSPENDED)
+    return mojom::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 == mojom::MemoryState::NORMAL)
+    return mojom::MemoryState::THROTTLED;
+  // TODO(bashi): Suspend background renderers after a certain period of time.
+#endif  // defined(OS_ANDROID)
+  return memory_state;
+}
+
 void MemoryCoordinator::SetDelegateForTesting(
     std::unique_ptr<MemoryCoordinatorDelegate> delegate) {
   CHECK(!delegate_);
   delegate_ = std::move(delegate);
 }
 
 void MemoryCoordinator::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 = mojom::MemoryState::NORMAL;
   child_info.is_visible = true;
   child_info.handle = std::move(handle);
 }
 
 MemoryCoordinator::ChildInfo::ChildInfo() {}
 
 MemoryCoordinator::ChildInfo::ChildInfo(const ChildInfo& rhs) {
   // This is a nop, but exists for compatibility with STL containers.
 }
 
 MemoryCoordinator::ChildInfo::~ChildInfo() {}
 
 }  // namespace content