CIO fails under high load

CIO.kt

import io.ktor.application.*
import io.ktor.client.*
import io.ktor.client.engine.cio.*
import io.ktor.client.request.*
import io.ktor.client.statement.*
import io.ktor.http.*
import io.ktor.response.*
import io.ktor.routing.*
import io.ktor.server.engine.*
import io.ktor.server.netty.*
import kotlinx.coroutines.*


suspend fun main() = withContext(Dispatchers.Default) {
    val batchCount = 100
    val batchSize = 100
    val threadCount = batchSize

    startServer()
    delay(1_000)

    HttpClient(CIO) {
        engine {
            threadsCount = threadCount
        }
    }.use { client ->
        repeat(batchCount) {
            coroutineScope {
                repeat(batchSize) {
                    launch { client.get<HttpResponse>("http://localhost:8080").readText() }
                }
            }
            println(it)
        }
    }
}

private fun startServer() {
    embeddedServer(Netty, port = 8080) {
        val data = " ".repeat(64_000)

        routing {
            get("/") {
                call.respondText(data, ContentType.Text.Plain)
            }
        }
    }.start()
}