perf(runner): drop 6 mktemp forks per cold start (#798)#801
Merged
Conversation
The deferred-output scratch files (failures, skipped, incomplete, risky, profile, rerun) each forked mktemp at cold start. Across the acceptance suite's ~258 nested bashunit runs that is ~1.5k forks and a large share of cold-start cost. Derive them from a single run-unique directory instead: random_str is fork-free and consumers create the files lazily via >> or guard reads with [ -s ], so pre-creation is unnecessary. 6 -> 0 mktemp forks per cold start; ~62ms -> ~50ms per nested run on bash 3.2. Closes #798
This was referenced Jul 15, 2026
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
🤔 Background
Related #798
Profiling the acceptance suite (~258 nested
bashunitruns) showed cold-start fork overhead, not per-test cost, dominating wall-clock. Each cold start forkedmktempsix times to create deferred-output scratch files.💡 Changes
mktempfork each —random_stris fork-free and consumers create the files lazily via>>.mktempforks per cold start; ~62ms → ~50ms per nested run on bash 3.2 (~3s off the acceptance suite).