Noticeable upfront cost of Dispatchers.Default about kotlinx.coroutines HOT 1 CLOSED

Worth noting that this code path is noticeable during our IDE startup, when Dispatchers.Default is initialized

Additional validation:

1. Running the trivial runBlocking + launch(Dispatchers.Default) with async-profiler start-n-profile.
   Note that it requires really high sampling interval

Flamegraph

Can be run as java -agentpath:/Users/qwwdfsad/workspace/async-profiler-3.0-macos/lib/libasyncProfiler.dylib=start,event=cpu,interval=100000,file=profile.html -jar main.jar.
In short, ~10% of the main code spent in the initialization of the first worker, ~70% of that time is spent in Random initialization

2. Startup is a subtle matter, so it's worth double-checking with something more deterministic.
   I've used -XX:+TraceBytecodes (note: you'll need fastdebug JDK for that).

The resulting flamegraph:

The same results w.r.t. relative cost

from kotlinx.coroutines.