Any one else notice that `CoroutineScheduler` seem...

# coroutines

[danny]

Any one else notice that CoroutineScheduler seems far too conservative about parking threads?

[danny]

I see a bunch of time spend in Thread.yield from cpuWorkerIdle - about double the system CPU time as user time. I must only have a few dozen coroutines running

[danny]

Guess this approximiates what I'm seeing -

fun main() {
    runBlocking {
        val count = AtomicInteger()
        val ints = produce<Int> {
            repeat(10) {
                launch(Dispatchers.Default) {
                    while (true) {
                        channel.send(count.incrementAndGet())
                    }
                }
            }
        }
        for (int in ints) {
            // Single consumer doing something expensive that can't be concurrent
            Thread.sleep(2)
        }
    }
}

[danny]

Vary the sleep in the loop consuming the channel and watch the scheduler back off and start parking threads

[danny]

message has been deleted

[danny]

message has been deleted

[Vsevolod Tolstopyatov [JB]]

https://github.com/Kotlin/kotlinx.coroutines/issues/840 yes, it is too conservative, this behaviour definitely will be fixed

[danny]

@Vsevolod Tolstopyatov [JB] is that something that's being actively worked on? I'd prefer to not have to rewrite to avoid the issue, but the system property only helps with Dispatchers.Default and not IO

[danny]

Also feels like there's more going on than just the spin/yield overhead - threads appear to spend far more time running than I'd expect at low throughput

[danny]

https://github.com/Kotlin/kotlinx.coroutines/issues/840#issuecomment-445958072

[Vsevolod Tolstopyatov [JB]]

Partial fix of this issue will be shipped in 1.1.0