Define thread priority enum and set thread priority for all threads in engine

Author: JsouLiang

fml/thread.cc

@@ -8,6 +8,7 @@
 
 #include <memory>
 #include <string>
+#include <utility>
 
 #include "flutter/fml/build_config.h"
 #include "flutter/fml/message_loop.h"
@@ -23,11 +24,24 @@
 
 namespace fml {
 
-Thread::Thread(const std::string& name) : joined_(false) {
+Thread::ThreadConfig::ThreadConfig(const std::string& name,
+                                   ThreadPriority priority)
+    : thread_name_(name), thread_priority_(priority) {}
+
+void Thread::ThreadConfig::SetCurrentThreadName() {
+  Thread::SetCurrentThreadName(thread_name_);
+}
+
+Thread::Thread(const std::string& name)
+    : Thread(ThreadConfig::DefaultConfigure(name)) {}
+
+Thread::Thread(std::unique_ptr<Thread::ThreadConfig> configurer)
+    : thread_configurer_(std::move(configurer)), joined_(false) {
   fml::AutoResetWaitableEvent latch;
   fml::RefPtr<fml::TaskRunner> runner;
-  thread_ = std::make_unique<std::thread>([&latch, &runner, name]() -> void {
-    SetCurrentThreadName(name);
+  thread_ = std::make_unique<std::thread>([&]() -> void {
+    thread_configurer_->SetCurrentThreadName();
+    thread_configurer_->SetCurrentThreadPriority();
     fml::MessageLoop::EnsureInitializedForCurrentThread();
     auto& loop = MessageLoop::GetCurrent();
     runner = loop.GetTaskRunner();

fml/thread.h

@@ -7,6 +7,7 @@
 
 #include <atomic>
 #include <memory>
+#include <string>
 #include <thread>
 
 #include "flutter/fml/macros.h"
@@ -16,18 +17,58 @@ namespace fml {
 
 class Thread {
  public:
-  explicit Thread(const std::string& name = "");
+  // Valid values for priority of Thread
+  enum class ThreadPriority : int {
+    // Suitable for threads that shouldn't disrupt high priority work.
+    BACKGROUND,
+    // Default priority level.
+    NORMAL,
+    // Suitable for threads which generate data for the display.
+    DISPLAY,
+    // Suitable for thread which raster data
+    RASTER,
+  };
+
+  /// The ThreadConfig is used for setting thread perorities
+  class ThreadConfig {
+   public:
+    explicit ThreadConfig(const std::string& name = "",
+                          ThreadPriority priority = ThreadPriority::NORMAL);
+
+    static std::unique_ptr<ThreadConfig> DefaultConfigure(
+        const std::string& name = "") {
+      return std::make_unique<ThreadConfig>(name);
+    }
+
+    ThreadPriority thread_priority() const { return thread_priority_; }
+
+    const std::string& thread_name() const { return thread_name_; }
+    virtual void SetCurrentThreadName();
+    virtual void SetCurrentThreadPriority() {}
+    virtual ~ThreadConfig() = default;
+
+   private:
+    const std::string thread_name_;
+    ThreadPriority thread_priority_;
+  };
+
+  explicit Thread(const std::string& name);
+
+  explicit Thread(std::unique_ptr<ThreadConfig> configurer =
+                      ThreadConfig::DefaultConfigure());
 
   ~Thread();
 
   fml::RefPtr<fml::TaskRunner> GetTaskRunner() const;
 
-  void Join();
-
   static void SetCurrentThreadName(const std::string& name);
 
+  void Join();
+
  private:
   std::unique_ptr<std::thread> thread_;
+  /// ThreadConfigure is used for setting thread configure some like `priority`
+  std::unique_ptr<ThreadConfig> thread_configurer_;
   fml::RefPtr<fml::TaskRunner> task_runner_;
   std::atomic_bool joined_;
 

shell/common/thread_host.cc

@@ -4,32 +4,73 @@
 
 #include "flutter/shell/common/thread_host.h"
 
+#include <algorithm>
+#include <memory>
+#include <string>
+#include <utility>
+
 namespace flutter {
 
+std::string ThreadHost::ThreadName(Type type, const std::string& prefix) {
+  switch (type) {
+    case Type::Platform:
+      return prefix + ".platform";
+    case Type::UI:
+      return prefix + ".ui";
+    case Type::IO:
+      return prefix + ".io";
+    case Type::RASTER:
+      return prefix + ".raster";
+    case Type::Profiler:
+      return prefix + ".profiler";
+  }
+}
+
+std::unique_ptr<fml::Thread> ThreadHost::CreateThread(
+    Type type,
+    ThreadHost::ThreadConfig configure) {
+  std::string name = ThreadName(type, name_prefix);
+  if (configure != nullptr) {
+    return std::make_unique<fml::Thread>(std::move(configure));
+  }
+  return std::make_unique<fml::Thread>(
+      fml::Thread::ThreadConfig::DefaultConfigure(name));
+}
+
 ThreadHost::ThreadHost() = default;
 
 ThreadHost::ThreadHost(ThreadHost&&) = default;
 
-ThreadHost::ThreadHost(std::string name_prefix_arg, uint64_t mask)
+ThreadHost::ThreadHost(std::string name_prefix_arg,
+                       uint64_t mask,
+                       ThreadHostConfig configure_host)
     : name_prefix(name_prefix_arg) {
   if (mask & ThreadHost::Type::Platform) {
-    platform_thread = std::make_unique<fml::Thread>(name_prefix + ".platform");
+    platform_thread =
+        CreateThread(ThreadHost::Type::Platform,
+                     std::move(configure_host.platform_configure));
   }
 
   if (mask & ThreadHost::Type::UI) {
-    ui_thread = std::make_unique<fml::Thread>(name_prefix + ".ui");
+    ui_thread = CreateThread(ThreadHost::Type::UI,
+                             std::move(configure_host.ui_configure));
   }
 
   if (mask & ThreadHost::Type::RASTER) {
-    raster_thread = std::make_unique<fml::Thread>(name_prefix + ".raster");
+    raster_thread = CreateThread(ThreadHost::Type::RASTER,
+                                 std::move(configure_host.raster_configure));
   }
 
   if (mask & ThreadHost::Type::IO) {
-    io_thread = std::make_unique<fml::Thread>(name_prefix + ".io");
+    io_thread = CreateThread(ThreadHost::Type::IO,
+                             std::move(configure_host.io_configure));
   }
 
   if (mask & ThreadHost::Type::Profiler) {
-    profiler_thread = std::make_unique<fml::Thread>(name_prefix + ".profiler");
+    profiler_thread =
+        CreateThread(ThreadHost::Type::Profiler,
+                     std::move(configure_host.profiler_configure));
+    ;
   }
 }
 

shell/common/thread_host.h

@@ -6,6 +6,7 @@
 #define FLUTTER_SHELL_COMMON_THREAD_HOST_H_
 
 #include <memory>
+#include <string>
 
 #include "flutter/fml/macros.h"
 #include "flutter/fml/thread.h"
@@ -22,6 +23,19 @@ struct ThreadHost {
     Profiler = 1 << 4,
   };
 
+  static std::string ThreadName(Type type, const std::string& prefix = "");
+
+  using ThreadConfig = std::unique_ptr<fml::Thread::ThreadConfig>;
+  /// The collection of all the thread configures, and we create custom thread
+  /// configure in engine to info the thread.
+  struct ThreadHostConfig {
+    ThreadConfig platform_configure;
+    ThreadConfig ui_configure;
+    ThreadConfig raster_configure;
+    ThreadConfig io_configure;
+    ThreadConfig profiler_configure;
+  };
+
   std::string name_prefix;
   std::unique_ptr<fml::Thread> platform_thread;
   std::unique_ptr<fml::Thread> ui_thread;
@@ -35,9 +49,14 @@ struct ThreadHost {
 
   ThreadHost& operator=(ThreadHost&&) = default;
 
-  ThreadHost(std::string name_prefix, uint64_t type_mask);
+  ThreadHost(std::string name_prefix,
+             uint64_t type_mask,
+             ThreadHostConfig configure_host = ThreadHostConfig());
 
   ~ThreadHost();
+
+ private:
+  std::unique_ptr<fml::Thread> CreateThread(Type type, ThreadConfig configure);
 };
 
 }  // namespace flutter

shell/platform/android/android_shell_holder.cc

@@ -32,6 +32,45 @@
 
 namespace flutter {
 
+/// Inheriting ThreadConfigurer and use Android platform thread API to configure
+/// the thread priorities
+class PlatformAndroidThreadConfig : public fml::Thread::ThreadConfig {
+ public:
+  using fml::Thread::ThreadConfig::ThreadConfig;
+
+  void SetCurrentThreadPriority() override {
+    switch (thread_priority()) {
+      case fml::Thread::ThreadPriority::BACKGROUND:
+        if (::setpriority(PRIO_PROCESS, 0, 10) != 0) {
+          FML_LOG(ERROR) << "Failed to set IO task runner priority";
+        }
+        break;
+      case fml::Thread::ThreadPriority::DISPLAY: {
+        if (::setpriority(PRIO_PROCESS, 0, -1) != 0) {
+          FML_LOG(ERROR) << "Failed to set UI task runner priority";
+        }
+        break;
+      }
+      case fml::Thread::ThreadPriority::RASTER: {
+        // Android describes -8 as "most important display threads, for
+        // compositing the screen and retrieving input events". Conservatively
+        // set the raster thread to slightly lower priority than it.
+        if (::setpriority(PRIO_PROCESS, 0, -5) != 0) {
+          // Defensive fallback. Depending on the OEM, it may not be possible
+          // to set priority to -5.
+          if (::setpriority(PRIO_PROCESS, 0, -2) != 0) {
+            FML_LOG(ERROR) << "Failed to set raster task runner priority";
+          }
+        }
+      }
+      default:
+        if (::setpriority(PRIO_PROCESS, 0, 0) != 0) {
+          FML_LOG(ERROR) << "Failed to set priority";
+        }
+    }
+  }
+};
+
 static PlatformData GetDefaultPlatformData() {
   PlatformData platform_data;
   platform_data.lifecycle_state = "AppLifecycleState.detached";
@@ -45,10 +84,23 @@ AndroidShellHolder::AndroidShellHolder(
   static size_t thread_host_count = 1;
   auto thread_label = std::to_string(thread_host_count++);
 
-  thread_host_ = std::make_shared<ThreadHost>();
-  *thread_host_ = {thread_label, ThreadHost::Type::UI |
-                                     ThreadHost::Type::RASTER |
-                                     ThreadHost::Type::IO};
+  auto ui_thread_name = flutter::ThreadHost::ThreadName(
+      flutter::ThreadHost::Type::UI, thread_label);
+  auto raster_thread_name = flutter::ThreadHost::ThreadName(
+      flutter::ThreadHost::Type::UI, thread_label);
+  auto io_thread_name = flutter::ThreadHost::ThreadName(
+      flutter::ThreadHost::Type::UI, thread_label);
+
+  thread_host_ = std::make_shared<ThreadHost>(
+      thread_label,
+      ThreadHost::Type::UI | ThreadHost::Type::RASTER | ThreadHost::Type::IO,
+      (flutter::ThreadHost::ThreadHostConfig){
+          .ui_configure = std::make_unique<PlatformAndroidThreadConfig>(
+              ui_thread_name, fml::Thread::ThreadPriority::DISPLAY),
+          .raster_configure = std::make_unique<PlatformAndroidThreadConfig>(
+              raster_thread_name, fml::Thread::ThreadPriority::RASTER),
+          .io_configure = std::make_unique<PlatformAndroidThreadConfig>(
+              io_thread_name, fml::Thread::ThreadPriority::BACKGROUND)});
 
   fml::WeakPtr<PlatformViewAndroid> weak_platform_view;
   Shell::CreateCallback<PlatformView> on_create_platform_view =
@@ -91,28 +143,6 @@ AndroidShellHolder::AndroidShellHolder(
                                     ui_runner,        // ui
                                     io_runner         // io
   );
-  task_runners.GetRasterTaskRunner()->PostTask([]() {
-    // Android describes -8 as "most important display threads, for
-    // compositing the screen and retrieving input events". Conservatively
-    // set the raster thread to slightly lower priority than it.
-    if (::setpriority(PRIO_PROCESS, gettid(), -5) != 0) {
-      // Defensive fallback. Depending on the OEM, it may not be possible
-      // to set priority to -5.
-      if (::setpriority(PRIO_PROCESS, gettid(), -2) != 0) {
-        FML_LOG(ERROR) << "Failed to set raster task runner priority";
-      }
-    }
-  });
-  task_runners.GetUITaskRunner()->PostTask([]() {
-    if (::setpriority(PRIO_PROCESS, gettid(), -1) != 0) {
-      FML_LOG(ERROR) << "Failed to set UI task runner priority";
-    }
-  });
-  task_runners.GetIOTaskRunner()->PostTask([]() {
-    if (::setpriority(PRIO_PROCESS, gettid(), 1) != 0) {
-      FML_LOG(ERROR) << "Failed to set IO task runner priority";
-    }
-  });
 
   shell_ =
       Shell::Create(GetDefaultPlatformData(),  // window data