Troubles with Shenandoah

[Roman Kennke]

> I did not need much load to trigger the Shenandoah failure, so
> perhaps
> stay low on the load (batch size = 10 or decrement it down to 1
> even),
> and make the runs longer (batch count = 1_000 -> 100_000).

Ok, I got it to fail with 20000 batch count.

I currently suspect that it's running out of code cache, and drops back
to interpreter. -XX:ReservedCodeCacheSize=2048m seems to fix it for me.
Can you verify it?

Not sure why code cache would not be cleaned though. We'll look into
that.

Thanks,
Roman