Scheduler: Enqueue non-JS-timer tasks into the unthrottled task runner

third_party/WebKit/Source/core/dom/TaskRunnerHelper.cpp

 // 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 "core/dom/TaskRunnerHelper.h"
 
 #include "core/dom/Document.h"
 #include "core/frame/LocalFrame.h"
 #include "platform/WebFrameScheduler.h"
 #include "platform/WebTaskRunner.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebThread.h"
 
 namespace blink {
 
 RefPtr<WebTaskRunner> TaskRunnerHelper::get(TaskType type, LocalFrame* frame) {
   // TODO(haraken): Optimize the mapping from TaskTypes to task runners.
   switch (type) {
     case TaskType::DOMManipulation:
     case TaskType::UserInteraction:
     case TaskType::HistoryTraversal:
     case TaskType::Embed:
     case TaskType::MediaElementEvent:
     case TaskType::CanvasBlobSerialization:
     case TaskType::RemoteEvent:
     case TaskType::WebSocket:
     case TaskType::Microtask:
-    case TaskType::PostedMessage:
     case TaskType::UnshippedPortMessage:
     case TaskType::FileReading:
     case TaskType::DatabaseAccess:
     case TaskType::Presentation:
     case TaskType::Sensor:
     case TaskType::PerformanceTimeline:
     case TaskType::Timer:
     case TaskType::UnspecedTimer:
     case TaskType::MiscPlatformAPI:
       return frame ? frame->frameScheduler()->timerTaskRunner()
                    : Platform::current()->currentThread()->getWebTaskRunner();
     case TaskType::UnspecedLoading:
     case TaskType::Networking:
       return frame ? frame->frameScheduler()->loadingTaskRunner()
                    : Platform::current()->currentThread()->getWebTaskRunner();
+    // We found throttling PostedMessage tasks may break existing web pages, so
+    // tentatively make it unthrottled.
+    // TODO(nhiroki): Consider to throttle this again maybe after making a
+    // mechanism that web pages can opt-out the throttling if throttling is not
+    // desirable.
+    case TaskType::PostedMessage:

[nhiroki, 2017/02/02 05:46:38]

As my comment on the issue[1], I'm still not sure why we move only PostedMessage
to the unthrottled task runner for a short-term fix. Why don't we move other
task types (other than Timer/UnspecedTimer) to the unthrottled task runner until
we have a mechanism to opt-out throttling from web pages or something else?

[1] https://bugs.chromium.org/p/chromium/issues/detail?id=684947#c18

[altimin, 2017/02/02 18:41:25]

+1, I'm particularly interested in unthrottling WebSocket messages.

[Sami, 2017/02/02 23:37:10]

Yeah, this seems like a reasonable step for now. If these other tasks are a
problem for CPU usage, we'll eventually find out once we improve our CPU
profiling and other metrics.

[nhiroki, 2017/02/03 15:07:34]

Acknowledged.

[nhiroki, 2017/02/03 15:07:34]

Acknowledged.

     case TaskType::Unthrottled:
       return frame ? frame->frameScheduler()->unthrottledTaskRunner()
                    : Platform::current()->currentThread()->getWebTaskRunner();
   }
   NOTREACHED();
   return nullptr;
 }
 
 RefPtr<WebTaskRunner> TaskRunnerHelper::get(TaskType type, Document* document) {
   return get(type, document ? document->frame() : nullptr);
 }
 
 RefPtr<WebTaskRunner> TaskRunnerHelper::get(
     TaskType type,
     ExecutionContext* executionContext) {
   return get(type, executionContext && executionContext->isDocument()
                        ? static_cast<Document*>(executionContext)
                        : nullptr);
 }
 
 RefPtr<WebTaskRunner> TaskRunnerHelper::get(TaskType type,
                                             ScriptState* scriptState) {
   return get(type, scriptState ? scriptState->getExecutionContext() : nullptr);
 }
 
 }  // namespace blink