Can somebody help me with a coroutines question. I was playing with something like shown in this gist: https://gist.github.com/mvucenovic/65359381a578e37558370cdf4e03ed9e. While running this on i7 with 8 cores, compiled to jvm 1.8 as target, coroutine code defined inside 'async' block was ~10x faster then calling any function doing the same thing inside async block (~700ms vs 8000ms). I know measuring performance with main method is terrible idea, but the difference in execution time is enormous in this gist Can somebody explain to me why is that happening?

misko: #coroutines

Results on my machine: Time with coro plain: 1027 ms Time with coro calling inline function: Time with coro calling suspend function: 35986 ms Time with coro calling normal function: 34813 ms Looks like first loop is replaced by compiler while in all other cases it doesn't. Also consider use JMH to get better results.

I've written some basic JMH benchmark to confirm it. I am not well versed in JMH benchmarks so I may have did something wrong, but it produced the same results (I too got as big as X35 differential without JMH, but JMH produced consistently ~X8 times slower results for non plain calls). I'll try to look at the byte code later.. It is strange to me. Tnx for trying it