Lightweight profiling with ghc-stack-profiler
summary
Lightweight sampling profiler implemented as a Haskell library that writes samples to the eventlog by periodically cloning RTS call stacks with the existing cloneThreadStack primitive and serialising frames. It doesn’t need the profiled RTS or recompilation of dependencies, but it requires -finfo-table-map for source locations and benefits from GHC 9.14 stack annotations to label regions. Output converts to SpeedScope via gstack-profiler-speedscope. Sampling is configurable (µs–ms); reported overheads in real workloads are around 20% and pure/lazy code can hide annotations.
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chapters (6)
- 0:00Introduction to the profiler
- 1:36Architecture and design
- 4:59Practical demonstration
- 14:25Stack annotations explained
- 20:49Strategic usage guidelines
- 22:40Summary and Q&A
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