PaSh: Light-touch Data-Parallel Shell Processing
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This paper presents PaSh, a system for parallelizing POSIX shell scripts. Given a script, PaSh converts it to a dataflow graph, performs a series of semantics-preserving program transformations that expose parallelism, and then converts the dataflow graph back into a script – one that adds POSIX constructs to explicitly guide parallelism coupled with PaSh-provided Unix-aware runtime primitives for addressing performance- and correctness-related issues. A lightweight annotation language allows command developers to express key parallelizability properties about their commands. An accompanying parallelizability study of POSIX and GNU commands – two large and commonly used groups – guides the annotation language and optimized aggregator library that PaSh uses. Finally, PaSh's PaSh's extensive evaluation over 44 unmodified Unix scripts shows significant speedups (0.89–61.1×, avg: 6.7×) stemming from the combination of its program transformations and runtime primitives.
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