By name: analyze-ci-speed description: Analyze compilation time and test durations from CI logs. Use when the user asks about slow builds, slow tests, or wants to optimize CI time.
Analyze CI Speed
Analyze compilation time and test durations from CI logs to identify optimization opportunities.
Prerequisites
ghCLI 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, nextest_all_features, 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