I noticed that

CoroutineScope.launch{ }

takes 40 ms. Isn’t this a bit much? Part of the point of launching is that you don’t need to wait for it, but apparently you do need to wait 40 ms as least

val scope = CoroutineScope(Dispatchers.Default)
    println(
        measureTimeMillis {
            scope.launch { }
        }
    )
// 40

This is done on a macbook pro 2021 m1 pro

Only on first launch? Maybe it’s just class loader penalty on first access

Ok, interesting, thanks

Also maybe the first use of

Dispatchers.Default

actually creates the threads in that pool

Yep, good point, Default/IO also will creates all thread pools on first access

val scope = CoroutineScope(newFixedThreadPoolContext(1, "test"))
println(
    measureTimeMillis {
        scope.launch { }
    }
)
println(
    measureTimeMillis {
        scope.launch { }
    }
)
println(
    measureTimeMillis {
        scope.launch { }
    }
)

44 22 0

But anyway, hard to say what takes this time without profiling, it worth to do if it’s a problem (for example there are many Dispatcher.Main for Android improvements, which optimizes first access)