[platform] Implement a worker pool

src/libplatform/default-platform.cc

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-#include "v8.h"
+#include "default-platform.h"
 
-#include "default-platform.h"
+#include <queue>
+
+// TODO(jochen): We should have our own version of checks.h.
+#include "../checks.h"
+// TODO(jochen): Why is cpu.h not in platform/?
+#include "../cpu.h"
+#include "task-queue.h"
+#include "worker-thread.h"
 
 namespace v8 {
 namespace internal {
 
-
-DefaultPlatform::DefaultPlatform() {}
+int DefaultPlatform::thread_pool_size_ = 0;
 
 
-DefaultPlatform::~DefaultPlatform() {}
+DefaultPlatform::DefaultPlatform() : thread_pool_(NULL), queue_(NULL) {}
+
+
+DefaultPlatform::~DefaultPlatform() {
+  if (thread_pool_) {
+    queue_->Terminate();
+    for (int i = 0; i < thread_pool_size_; ++i) {
+      thread_pool_[i]->Join();
+      delete thread_pool_[i];
+    }
+    delete[] thread_pool_;
+    delete queue_;
+  }
+}
+
+
+// static
+void DefaultPlatform::SetThreadPoolSize(int thread_pool_size) {
+  ASSERT(thread_pool_size >= 0);
+  // TODO(jochen): If this wasn't a static member, we should
+  // ASSERT(!thread_pool_);
+  thread_pool_size_ = thread_pool_size;
+}
 
 void DefaultPlatform::CallOnBackgroundThread(Task *task,
                                              ExpectedRuntime expected_runtime) {
-  // TODO(jochen): implement.
-  task->Run();
-  delete task;
+  EnsureThreadPoolStarted();
+  queue_->Append(task);
 }
 
 
 void DefaultPlatform::CallOnForegroundThread(v8::Isolate* isolate, Task* task) {
   // TODO(jochen): implement.
   task->Run();
   delete task;
 }
 
 
+void DefaultPlatform::EnsureThreadPoolStarted() {
+  if (thread_pool_) return;
+  queue_ = new TaskQueue;
+  if (thread_pool_size_ < 1)
+    thread_pool_size_ = CPU::NumberOfProcessorsOnline();
+  thread_pool_size_ = Max(Min(thread_pool_size_, 4), 1);

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

Wouldn't it be better to do some sanity checks/clamping in
DefaultPlatform::SetThreadPoolSize instead? Furhtermore, it might be nice to
have a flag for the hardcoded limit of 4.

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

We'd need to do the clamping and sanity check here anyway, in case
SetThreadPoolSize was never invoked.
I dunno. I'd add the flag when it's needed.

+
+  thread_pool_ = new WorkerThread*[thread_pool_size_];
+
+  for (int i = 0; i < thread_pool_size_; ++i) {
+    thread_pool_[i] = new WorkerThread(queue_);
+    thread_pool_[i]->Start();
+  }
+}
+
 } }  // namespace v8::internal