Home Parallel Performance Tuning for Haskell Parallel Performance Tuning for Haskell. Don Jones Jr., Simon Marlow, and Satnam Singh. 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. The paper illustrates the use of ThreadScope through a number of case studies, and describes some useful methodologies for parallelizing Haskell programs. Comment viewing options Flat list - collapsed Flat list - expanded Threaded list - collapsed Threaded list - expanded Date - newest first Date - oldest first Select your preferred way to display the comments and click "Save settings" to activate your changes.