aw: Improve idle task scheduling

android_webview/browser/shared_renderer_state.cc

Index: android_webview/browser/shared_renderer_state.cc
diff --git a/android_webview/browser/shared_renderer_state.cc b/android_webview/browser/shared_renderer_state.cc
index 7c7238e7d2053442c97e3462e9e5c23424724482..1389e043377f90b61e64c62a98c59a8cd7354e09 100644
--- a/android_webview/browser/shared_renderer_state.cc
+++ b/android_webview/browser/shared_renderer_state.cc
@@ -6,10 +6,65 @@
 
 #include "android_webview/browser/browser_view_renderer_client.h"
 #include "base/bind.h"
+#include "base/lazy_instance.h"
 #include "base/location.h"
 
 namespace android_webview {
 
+namespace internal {
+
+class RequestDrawGLTracker {
+ public:
+  RequestDrawGLTracker();
+  bool ShouldRequestOnNoneUiThread(SharedRendererState* state);
+  bool ShouldRequestOnUiThread(SharedRendererState* state);
+  void DidRequestOnUiThread();
+  void DidDrawGLProcess();
+
+ private:
+  base::Lock lock_;
+  SharedRendererState* pending_ui_;
+  SharedRendererState* pending_non_ui_;
+};
+
+RequestDrawGLTracker::RequestDrawGLTracker()
+    : pending_ui_(NULL), pending_non_ui_(NULL) {
+}
+
+bool RequestDrawGLTracker::ShouldRequestOnNoneUiThread(
+    SharedRendererState* state) {
+  base::AutoLock lock(lock_);
+  if (pending_ui_ || pending_non_ui_)

[hush (inactive), 2014/08/07 22:14:27]

this means there should be only at most one pending request globally, at any
specific time. Right?

What happens if you one request pending on UI and another pending on non-UI
thread?

[boliu, 2014/08/07 22:21:35]

That's the goal. But it's not quite true.

Right now there can be two RequestDrawGL calls before the first
DrawGL(kModeProcess) comes back. Here's how it happens:

Non-ui thread post UI thread to request gl, it runs.
UI thread request gl, it runs

But right now it's capped at just 2. This is good enough for now apparently.
If UI comes first, it cancels the non-UI one. If the non-UI one comes first,
both goes through as above.

+    return false;
+  pending_non_ui_ = state;
+  return true;
+}
+
+bool RequestDrawGLTracker::ShouldRequestOnUiThread(SharedRendererState* state) {
+  base::AutoLock lock(lock_);
+  if (pending_non_ui_) {
+    pending_non_ui_->ResetRequestDrawGLCallback();
+    pending_non_ui_ = NULL;
+  }
+  if (pending_ui_)
+    return false;
+  pending_ui_ = state;
+  return true;
+}
+
+void RequestDrawGLTracker::DidDrawGLProcess() {
+  base::AutoLock lock(lock_);
+  pending_non_ui_ = NULL;
+  pending_ui_ = NULL;
+}
+
+}  // namespace internal
+
+namespace {

[hush (inactive), 2014/08/07 22:14:27]

an empty line after this line?

+base::LazyInstance<internal::RequestDrawGLTracker> g_request_draw_gl_tracker =
+    LAZY_INSTANCE_INITIALIZER;
+}
+
 DrawGLInput::DrawGLInput() : width(0), height(0) {
 }
 
@@ -27,6 +82,7 @@ SharedRendererState::SharedRendererState(
       share_context_(NULL) {
   DCHECK(ui_loop_->BelongsToCurrentThread());
   DCHECK(client_on_ui_);
+  ResetRequestDrawGLCallback();
 }
 
 SharedRendererState::~SharedRendererState() {
@@ -39,17 +95,37 @@ bool SharedRendererState::CurrentlyOnUIThread() {
 
 void SharedRendererState::ClientRequestDrawGL() {
   if (ui_loop_->BelongsToCurrentThread()) {
+    if (!g_request_draw_gl_tracker.Get().ShouldRequestOnUiThread(this))
+      return;
     ClientRequestDrawGLOnUIThread();
   } else {
-    ui_loop_->PostTask(
-        FROM_HERE,
-        base::Bind(&SharedRendererState::ClientRequestDrawGLOnUIThread,
-                   ui_thread_weak_ptr_));
+    if (!g_request_draw_gl_tracker.Get().ShouldRequestOnNoneUiThread(this))
+      return;
+    base::Closure callback;
+    {
+      base::AutoLock lock(lock_);
+      callback = request_draw_gl_closure_;
+    }
+    ui_loop_->PostTask(FROM_HERE, callback);
   }
 }
 
+void SharedRendererState::DidDrawGLProcess() {
+  g_request_draw_gl_tracker.Get().DidDrawGLProcess();
+}
+
+void SharedRendererState::ResetRequestDrawGLCallback() {
+  DCHECK(ui_loop_->BelongsToCurrentThread());
+  base::AutoLock lock(lock_);
+  request_draw_gl_cancelable_closure_.Reset(
+      base::Bind(&SharedRendererState::ClientRequestDrawGLOnUIThread,
+                 base::Unretained(this)));
+  request_draw_gl_closure_ = request_draw_gl_cancelable_closure_.callback();
+}
+
 void SharedRendererState::ClientRequestDrawGLOnUIThread() {
   DCHECK(ui_loop_->BelongsToCurrentThread());
+  ResetRequestDrawGLCallback();
   if (!client_on_ui_->RequestDrawGL(NULL, false)) {
     LOG(ERROR) << "Failed to request GL process. Deadlock likely";
   }