hS: Speculative Script Reordering at Subprocess Granularity
Talkat 20th USENIX Symposium on Operating Systems Design and Implementation (OSDI '26) · 2026-07-13..07-15·
summary
hS is a system that speculatively executes shell commands out of order by running command instances in sandboxed layers and tracing system calls to detect real read/write dependencies, then selectively commits or discards effects. It preprocesses scripts into a runtime-callback skeleton, uses a runtime orchestrator (formally checked with an Alloy model) to restart violated executions, and handles network and file side effects. On 49 real scripts hS speeds up 42 (up to 9.3× over bash and up to 7× over PaSh) while remaining annotation-free.
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chapters (8)
- 0:00HS introduction
- 1:22Shell script performance
- 2:49Optimization limits
- 5:38Reordering commands
- 7:24Safe speculation
- 9:53HS runtime design
- 11:57Performance results
- 14:48Summary and availability
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