Parallel Performance Tuning for Haskell

Very interesting work with implications for integration into more mainstream runtimes... In general, runtime support for parallel tuning is necessary going forward. The Many Core age has only just begun... This paper is a great read.

Parallel Haskell programming has entered the mainstream with support now included in GHC for multiple parallel programming models, along with multicore execution support in the runtime. However, tuning programs for parallelism is still something of a black art. Without much in the way of feedback provided by the runtime system, it is a matter of trial and error combined with experience to achieve good parallel speedups.

This paper describes an early prototype of a parallel profiling system for multicore programming with GHC. The system comprises three parts: fast event tracing in the runtime, a Haskell library for reading the resulting trace files, and a number of tools built on this library for presenting the information to the programmer. We focus on one tool in particular, a graphical timeline browser called ThreadScope.