Analyze CI Speed

Analyze compilation time and test durations from CI logs to identify optimization opportunities.

Prerequisites

• gh CLI installed and authenticated (gh auth login)

Instructions

Step 1: Get Recent Workflow Runs

Get latest successful run from dev branch:

gh run list --workflow=Rust --branch=dev --limit=1 --status=success --json databaseId,conclusion,headSha,createdAt

Step 2: Download Test Job Logs

Get test jobs (nextest, nextestallfeatures, coverage):

gh run view <run-id> --json jobs --jq '.jobs[] | select(.name == "nextest" or .name == "nextest_all_features" or .name == "coverage") | {id: .databaseId, name: .name}'

Download logs, stripping ANSI codes:

mkdir -p ci-logs/speed-analysis/
gh run view --job <job-id> --log | perl -pe 's/\e\[[0-9;]*m//g' > ci-logs/speed-analysis/<job_name>.log

Step 3: Extract Compilation Time

Search for cargo build summary in logs:

Finished ... in Xm Ys

Also look for incremental compilation info and cache hit rates.

Step 4: Extract Test Durations

Parse nextest output for test durations. Look for patterns like:

PASS [   1.234s] crate_name::module::test_name
SLOW [  15.678s] crate_name::module::slow_test

Extract all test durations and sort to find top 10 slowest tests.

Step 5: Analyze and Report

Provide summary:

• Total compilation time
• Top 10 slowest tests with durations
• Any tests marked as SLOW by nextest
• Recommendations:

- Tests that could be optimized or parallelized - Crates with long compilation times - Potential for better caching

Notes

• Run on successful builds to get complete timing data
• Compare across runs to identify regressions