Reland "Throttle resource message requests during user interaction"

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index ef6dae73a17d9089b2dd3944daba5ce839042c19..ca498b7125ba3b0fccd01dddd3d9e87c4861fa62 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -103,6 +103,7 @@
 #include "content/renderer/render_process_impl.h"
 #include "content/renderer/render_view_impl.h"
 #include "content/renderer/renderer_blink_platform_impl.h"
+#include "content/renderer/resource_dispatch_throttler.h"
 #include "content/renderer/scheduler/renderer_scheduler.h"
 #include "content/renderer/service_worker/embedded_worker_context_message_filter.h"
 #include "content/renderer/service_worker/embedded_worker_dispatcher.h"
@@ -195,6 +196,16 @@ namespace {
 const int64 kInitialIdleHandlerDelayMs = 1000;
 const int64 kLongIdleHandlerDelayMs = 30*1000;
 
+#if defined(OS_ANDROID)
+// On Android, resource messages can each take ~1.5ms to dispatch on the browser
+// IO thread. Limiting the message rate to 3/frame at 60hz ensures that the
+// induced work takes but a fraction (~1/4) of the overall frame budget.
+const int kMaxResourceRequestsPerFlushWhenThrottled = 3;
+#else
+const int kMaxResourceRequestsPerFlushWhenThrottled = 8;
+#endif
+const double kThrottledResourceRequestFlushPeriodS = 1. / 60.;
+
 // Maximum allocation size allowed for image scaling filters that
 // require pre-scaling. Skia will fallback to a filter that doesn't
 // require pre-scaling if the default filter would require an
@@ -478,6 +489,12 @@ void RenderThreadImpl::Init() {
   channel()->SetListenerTaskRunner(renderer_scheduler_->DefaultTaskRunner());
   embedded_worker_dispatcher_.reset(new EmbeddedWorkerDispatcher());
 
+  resource_dispatch_throttler_.reset(new ResourceDispatchThrottler(

[alex clarke (OOO till 29th), 2015/01/26 17:15:59]

I wonder if we should have a FIXME comment since in an ideal world all
operations on the the IO thread would be fast and we wouldn't need to do this.

[jdduke (slow), 2015/01/26 20:14:48]

That's a good point, yeah, I'll put a note in ResourceDispatchThrottler that it
should eventually go away entirely.

+      static_cast<RenderThread*>(this), renderer_scheduler_.get(),
+      base::TimeDelta::FromSecondsD(kThrottledResourceRequestFlushPeriodS),
+      kMaxResourceRequestsPerFlushWhenThrottled));
+  resource_dispatcher()->set_message_sender(resource_dispatch_throttler_.get());
+
   media_stream_center_ = NULL;
 
   db_message_filter_ = new DBMessageFilter();