ThreadScope is a graphical thread profiler and debugger for Haskell.
The Threadscope program attaches to a running Haskell program, allowing 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.
ThreadScope is now available pre-packaged for Arch Linux via AUR. It builds on the newly cabalized GTK libraries, such as haskell-cairo.
For information on how to use ThreadScope to improve the performance of your multicore Haskell programs, see the references:
- Parallel Performance Tuning for Haskell.
- Runtime Support for Multicore Haskell.
- A Tutorial on Parallel and Concurrent Programming in Haskell.
- A video by Simon Marlow which demos ThreadScope.
Arch Linux and Haskell 
That’s great, unfortunately I am getting an error when trying to install it. See below:
Configuring ghc-events-0.4.0.0…
Setup: At least the following dependencies are missing:
mtl >=1.1 && ERROR: A failure occurred in build().
Aborting…
==> ERROR: Makepkg was unable to build haskell-ghc-events.
==> Restart building haskell-ghc-events ? [y/N]
==> ——————————————-
==>
==> Restart building threadscope ? [y/N]
==> ————————————