ThreadScope is a graphical viewer for thread profile information
generated by the Glasgow Haskell Compiler (GHC).

The ThreadScope program allows us to debug the parallel performance of
Haskell programs.  Using Threadscope we can check to see that work is
well balanced across the available processors and spot performance
issues relating to garbage collection or poor load balancing.

WWW: https://www.haskell.org/haskellwiki/ThreadScope