如何在 Kotlin Native 中设置协程调度程序的线程优先级

Question

I'm using coroutines in my multiplatform (android + iOS) application. To be able to use multithreaded coroutines, I'm using native-mt builds. So now I need to create a CoroutineDispatcher which runs on a hight priority thread. On android I'm doing it like this

val thread = HandlerThread("myThread", -20).also {
    it.start()
}
val highPriorityDispatcher = Handler(thread.looper).asCoroutineDispatcher()

Is there a way to create a similar hight-priority dispatcher on iOS?

First what I tried is to create a new dispatcher using newSingleThreadContext . In k/n the resulting dispatcher exposes its Worker , but I have not found any ways to set worker priority. Also I tried to raise thread priority with the setThreadPriority method:

val highPriorityDispatcher = newSingleThreadContext("myThread").also {
    scope.launch(it){
        NSThread.setThreadPriority(1.0)
    }
}

But it did not seem to have the proper effect.

I'm thinking about writing a custom dispatcher using dispatch_queue , but it seems to be a non-trivial task. So any help to find an easier way to solve this problem would be appreciated.

Answer 1

Ok, actually it seems I was wrong.

val highPriorityDispatcher = newSingleThreadContext("myThread").also {
    scope.launch(it){
        NSThread.setThreadPriority(1.0)
    }
}

does the job and actually changes the priority, confirmed in the iOS profiler. At the end I also added

  pthread_set_qos_class_self_np(QOS_CLASS_USER_INTERACTIVE, 0)

call to set the QoS. I used the pthread version, because here it says that

NSThread possesses a qualityOfService property, of type NSQualityOfService. This class will not infer a QoS based on the context of its execution, so the value of this property may only be changed before the thread has started. Reading the qualityOfService of a thread at any time provides its current value.