Do V8 GC ASAP if system memory is pressured

third_party/WebKit/Source/core/workers/WorkerThread.cpp

Index: third_party/WebKit/Source/core/workers/WorkerThread.cpp
diff --git a/third_party/WebKit/Source/core/workers/WorkerThread.cpp b/third_party/WebKit/Source/core/workers/WorkerThread.cpp
index 7b31a57783e4fec5f853f6ca1d08b36bd671f2a1..04f79327f5d29667a506f42feec5a94ec818638b 100644
--- a/third_party/WebKit/Source/core/workers/WorkerThread.cpp
+++ b/third_party/WebKit/Source/core/workers/WorkerThread.cpp
@@ -54,6 +54,8 @@
 
 namespace blink {
 
+std::set<v8::Isolate*>* WorkerThread::gIsolates = nullptr;
+
 class WorkerMicrotaskRunner : public WebThread::TaskObserver {
 public:
     explicit WorkerMicrotaskRunner(WorkerThread* workerThread)
@@ -210,6 +212,9 @@ void WorkerThread::initialize(PassOwnPtr<WorkerThreadStartupData> startupData)
         backingThread().addTaskObserver(m_microtaskRunner.get());
 
         m_isolate = initializeIsolate();
+        if (!gIsolates)
+            gIsolates = new std::set<v8::Isolate*>();
+        gIsolates->insert(m_isolate);

[kinuko, 2016/04/11 09:30:40]

For compositor worker (where single thread is shared by multiple workers)
initializeIsolate() returns the same isolate for multiple times, and
destroyIsolate() may not be actually destroying the isolate yet if there're
other compositor workers running on the same thread.

We're working on making the part slightly cleaner but for the time being.. maybe
destroyIsolate() could return a bool value that indicates if it actually
destroyed the isolate or not?

[hong.zheng, 2016/04/15 06:05:57]

use WorkerBackingThread instead

         // Optimize for memory usage instead of latency for the worker isolate.
         m_isolate->IsolateInBackgroundNotification();
         m_workerGlobalScope = createWorkerGlobalScope(startupData);
@@ -277,6 +282,7 @@ void WorkerThread::performShutdownTask()
     willDestroyIsolate();
     shutdownBackingThread();
     destroyIsolate();
+    gIsolates->erase(m_isolate);
     m_isolate = nullptr;
 
     m_microtaskRunner = nullptr;
@@ -501,4 +507,10 @@ void WorkerThread::stopRunningDebuggerTasksOnPause()
     m_pausedInDebugger = false;
 }
 
+// static
+std::set<v8::Isolate*>* WorkerThread::workerThreadIsolates()
+{
+    return gIsolates;

[kinuko, 2016/04/11 09:30:40]

We seem to be accessing this set from multiple threads without locking?

[hong.zheng, 2016/04/15 06:05:57]

Done.

+}
+
 } // namespace blink