Strange behaviour on half-occupied heap

[Aleksey Shipilev]

On 08/29/2018 06:09 PM, Simon Ogorodnik wrote:
> I doubled heap to 4G, but situation still reproduces after a bit more time

Hold on for the fixes then. My IDEA/CLion runs fine with current 8u builds, though. I have a few
test cases where the same thing might reproduce.

> Maybe there also some problem with marking Why those garbage is marked with ‘Live’ color in
> visualiser and not getting into CSet? Is it actually live and HPROF heap dump is incorrect?
You cannot really tell that from Visualizer: it uses the gradient to show the liveness.

But conceptually, what GC thinks about the liveness is the approximation anyway, which is only
reliable right after the concurrent mark if there were no allocations during the cycle. So, whatever
heap dump say is probably correct, but there is no way for GC to know that reliably at all times.
Otherwise, there would be no such thing as "floating garbage".

Thanks,
-Aleksey