It's doing other enqueued work

# coroutines

[jw]

It's doing other enqueued work

[Ruckus]

What about when there isn't any enqueued work (such as a single delay)? Does it just do a busy loop? For example, if I do

suspend fun main() {
    delay(10_000L)
}

will it just eat the CPU for 10 seconds, or does it wait and notify the thread?

[jw]

that's an implementation detail. i suspect it parks the thread and wakes it up if any new work is scheduled. Or perhaps if the gap is small enough it does a busy wait or calls Thread.onSpinWait

[elizarov]

It parks. No spin wait optimization at the moment for runBlocking https://github.com/Kotlin/kotlinx.coroutines/blob/master/core/kotlinx-coroutines-core/src/Builders.kt#L72

[Ruckus]

I'm not entirely sure what parking is. It seems I have much to learn about coroutines.

[elizarov]

Parking has nothing to do with coroutines. It is just a low level mechanism that “suspends a thread” in OS. You don’t have to know about it if you are using coroutines.

[Ruckus]

Ah, that makes much more sense. Thanks!

[louiscad]

For future reference, here's the permalink for the line of code that Roman linked: https://github.com/Kotlin/kotlinx.coroutines/blob/46741db4b0c2863475d5cc6fc75eafadd8e6199d/core/kotlinx-coroutines-core/src/Builders.kt#L72