Lower JS Thread Priority by 10

Summary:
## Changelog: [Internal]: [Threading][Added] - Add option to change thread priority
D73074402 handles lowering priority for IWM js and granite threads. this diff handles lowering priority for in game panel js thread

JS thread inherits parent thread priority by default
lowering priority by 10

Reviewed By: rshest

Differential Revision: D72842049

fbshipit-source-id: 6797f7c8406a410956c64bb08a12d2b26c100040

Author: Eugene Lin

packages/react-native/ReactCxxPlatform/react/threading/MessageQueueThreadImpl.h

@@ -25,6 +25,8 @@ constexpr char MessageQueueThreadFactoryKey[] = "MessageQueueThreadFactoryKey";
 class MessageQueueThreadImpl : public MessageQueueThread {
  public:
   MessageQueueThreadImpl() noexcept = default;
+  explicit MessageQueueThreadImpl(int priorityOffset) noexcept
+      : taskDispatchThread_("MessageQueue", priorityOffset) {}
 
   ~MessageQueueThreadImpl() noexcept override = default;
 

packages/react-native/ReactCxxPlatform/react/threading/TaskDispatchThread.cpp

@@ -7,24 +7,43 @@
 
 #include "TaskDispatchThread.h"
 
+#include <folly/portability/SysResource.h>
 #include <folly/system/ThreadName.h>
 #include <chrono>
 #include <future>
 #include <utility>
 
+#include <glog/logging.h>
+
 #ifdef ANDROID
 #include <fbjni/fbjni.h>
+#include <sys/syscall.h>
 #endif
 
 namespace facebook::react {
 
-TaskDispatchThread::TaskDispatchThread(std::string threadName) noexcept
+TaskDispatchThread::TaskDispatchThread(
+    std::string threadName,
+    int priorityOffset) noexcept
     : threadName_(std::move(threadName)) {
 #ifdef ANDROID
   // Attaches the thread to JVM just in case anything calls out to Java
   thread_ = std::thread([&]() {
-    facebook::jni::ThreadScope::WithClassLoader([&]() { loop(); });
+    facebook::jni::ThreadScope::WithClassLoader([&]() {
+      int result = setpriority(
+          PRIO_PROCESS,
+          static_cast<pid_t>(::syscall(SYS_gettid)),
+          priorityOffset);
+
+      if (result != 0) {
+        LOG(INFO) << " setCurrentThreadPriority failed with pri errno: "
+                  << errno;
+      }
+
+      loop();
+    });
   });
+
 #else
   thread_ = std::thread(&TaskDispatchThread::loop, this);
 #endif

packages/react-native/ReactCxxPlatform/react/threading/TaskDispatchThread.h

@@ -25,7 +25,10 @@ class TaskDispatchThread {
   using TaskFn = std::function<void()>;
   using TimePoint = std::chrono::time_point<std::chrono::system_clock>;
 
-  TaskDispatchThread(std::string threadName = "") noexcept;
+  TaskDispatchThread(
+      std::string threadName = "",
+      int priorityOffset = 0) noexcept;
+
   ~TaskDispatchThread() noexcept;
 
   /** Return true if the current thread is the same as this looper's thread. */