[platform] Implement a worker pool

src/libplatform/default-platform.h

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-#ifndef V8_DEFAULT_PLATFORM_H_
-#define V8_DEFAULT_PLATFORM_H_
+#ifndef V8_LIBPLATFORM_DEFAULT_PLATFORM_H_
+#define V8_LIBPLATFORM_DEFAULT_PLATFORM_H_
 
-#include "v8.h"
+#include "../../include/v8-platform.h"
+// TODO(jochen): We should have our own version of globals.h.
+#include "../globals.h"
 
 namespace v8 {
 namespace internal {
 
+class TaskQueue;
+class Thread;
+class WorkerThread;
+
 class DefaultPlatform : public Platform {
  public:
   DefaultPlatform();
   virtual ~DefaultPlatform();
 
+  // TODO(jochen): This shouldn't be static.
+  static void SetThreadPoolSize(int thread_pool_size);
+
   // v8::Platform implementation.
   virtual void CallOnBackgroundThread(
       Task *task, ExpectedRuntime expected_runtime) V8_OVERRIDE;
   virtual void CallOnForegroundThread(v8::Isolate *isolate,
                                       Task *task) V8_OVERRIDE;
 
  private:
+  void EnsureThreadPoolStarted();
+
+  WorkerThread** thread_pool_;
+  // TODO(jochen): This shouldn't be a static.

[Sven Panne, 2013/12/05 10:04:11]

What's the reason for "static"? Wouldn't it be easier to have a
std::list<WorkerThread*> here? Furthermore, the WorkerThreads are owned by the
list, so it might be nice to have a std::list<WorkerThread>, but I guess we
would have to do some massaging to the WorkerThread class hierarchy to make the
threads auto-join on destruction.

[jochen (gone - plz use gerrit), 2013/12/05 12:58:53]

The reason for static is that currently v8 magically creates the platform
internally.

When the embedder creates the platform, it can just be a method.

The way it is now, we create default platform when initializing the default
isolate, however, the resource constraints are set before the default isolate is
initialized.

I've changed worker thread to auto-join on destruction.

Using list<WorkerThread> would mean that they need to be copyable etc..

+  static int thread_pool_size_;
+  TaskQueue* queue_;
+
   DISALLOW_COPY_AND_ASSIGN(DefaultPlatform);
 };
 
 
 } }  // namespace v8::internal
 
 
-#endif  // V8_DEFAULT_PLATFORM_H_
+#endif  // V8_LIBPLATFORM_DEFAULT_PLATFORM_H_