Ln 811 Performance Profiler

Paths: File paths (references/, ../ln-*) are relative to this skill directory.

ln-811-performance-profiler

Type: L3 Worker Category: 8XX Optimization

Runtime profiler that executes the optimization target, measures multiple metrics (CPU, memory, I/O, time), instruments code for per-function breakdown, and produces a standardized performance map from real data.

Overview

Workflow

Phases: Test Discovery → Baseline Run → Static Analysis → Deep Profile → Performance Map → Report

Phase 0: Test Discovery/Creation

MANDATORY READ: Load references/ci_tool_detection.md for test framework detection. MANDATORY READ: Load references/benchmark_generation.md for auto-generating benchmarks when none exist.

Find or create commands that exercise the optimization target. Two outputs: test_command (profiling/measurement) and e2e_test_command (functional safety gate).

Step 1: Discover test_command

E2E discovery protocol (stop at first match):

Test creation (if no existing test found):

Step 2: Discover e2e_test_command

If test_command came from E2E discovery (Step 1 priority 2): e2e_test_command = test_command.

Otherwise, run E2E discovery protocol again (same 3-priority table) to find a separate functional safety test.

If not found: e2e_test_command = null, log: WARNING: No e2e test covers {entry_point}. Full test suite serves as functional gate.

Output

Phase 1: Baseline Run (Multi-Metric)

Run test_command with system-level profiling. Capture simultaneously:

Baseline Protocol

Monitor for Profiler Runs (Claude Code 2.1.98+)

MANDATORY READ: Load references/monitor_integration_pattern.md

During baseline and deep profile runs: Monitor(command="{test_command} 2>&1", timeout_ms=300000, description="profiler run N")

Detect crashes or infinite loops immediately. Fallback: Bash with timeout.

Phase 2: Static Analysis → Instrumentation Points

MANDATORY READ: Load bottleneck_classification.md

Trace call chain from code + build suspicion stack. Purpose: guide WHERE to instrument in Phase 3.

Step 1: Trace Call Chain

Starting from entry point, trace depth-first (max depth 5). At each step, READ the full function body.

Cross-service tracing: If service_topology is available from coordinator and a step makes an HTTP/gRPC call to another service whose code is accessible:

Record service: "{service_name}" on each step to track which service owns it. The performance_map steps tree can span multiple services.

Depth-First Rule: If code of the called service is accessible — ALWAYS profile INSIDE. NEVER classify an accessible service as "External/slow" without profiling its internals. "Slow" is a symptom, not a diagnosis.

5 Whys for each bottleneck: Before reporting a bottleneck, chain "why?" until you reach config/architecture level:

1. "What is slow?" → alignment service (5.9s) 2. "Why?" → 6 pairs × ~1s each 3. "Why ~1s per pair?" → O(n²) mwmf computation 4. "Why O(n²)?" → library default, not production config 5. "Why default?" → matching_methods not configured → root cause = config

Step 2: Classify & Suspicion Scan

For each step, classify by type (CPU, I/O-DB, I/O-Network, I/O-File, Architecture, External, Cache) and scan for performance concerns.

Suspicion checklist (minimum, not limitation):

Step 2b: Suspicion Deduplication

MANDATORY READ: Load references/output_normalization.md

After generating suspicions across all call chain steps, normalize and deduplicate per §1-§2:

• Normalize suspicion descriptions (replace specific values with placeholders)
• Group identical suspicions across different steps → merge into single entry with affected_steps: [list]
• Example: "Missing connection pooling" found in steps 1.1, 1.2, 1.3 → one suspicion with affected_steps: ["1.1", "1.2", "1.3"]

Step 3: Verify & Map to Instrumentation Points

FOR each suspicion:
  1. VERIFY: follow code to confirm or dismiss
  2. VERDICT: CONFIRMED → map to instrumentation point | DISMISSED → log reason
  3. For each CONFIRMED suspicion, identify:
     - function to wrap with timing
     - I/O call to count
     - memory allocation to track

Profiler Selection (per stack)

Stack detection: per references/ci_tool_detection.md.

Phase 3: Deep Profile

Profiler Hierarchy (escalate as needed)

Step 1: Non-Invasive Profiling (preferred)

Run test_command with Level 1 profiler to get per-function breakdown without code changes.

Step 2: Escalation Decision

After Level 1 profiler run, evaluate result against suspicion stack from Phase 2:

Stop Conditions (Profiler Escalation)

Step 3: Targeted Instrumentation (proactive)

Add timing/logging along the call stack at instrumentation points identified in Phase 2 Step 3:

1. FOR each CONFIRMED suspicion without measured data:
     Add timing wrapper around target function/I/O call
     Add counter for I/O round-trips if network/DB suspected
     (cross-service: instrument in the correct service's codebase)
2. Re-run test_command (3 runs, median)
3. Collect per-function measurements from logs
4. Record list of instrumented files (may span multiple services)

KEEP instrumentation in place. The executor reuses it for post-optimization per-function comparison, then cleans up after strike. Report instrumented_files in output.

Phase 4: Build Performance Map

Standardized format — feeds into .hex-skills/optimization/{slug}/context.md for downstream consumption.

performance_map:
  test_command: "uv run pytest tests/automated/e2e/test_example.py -s"
  baseline:
    wall_time_ms: 7280
    cpu_time_ms: 850
    memory_peak_mb: 256
    memory_delta_mb: 45
    io_read_bytes: 1200000
    io_write_bytes: 500000
    http_round_trips: 13
  steps:                          # service field present only in multi-service topology
    - id: "1"
      function: "process_job"
      location: "app/services/job_processor.py:45"
      service: "api"             # optional — which service owns this step
      wall_time_ms: 7200
      time_share_pct: 99
      type: "function_call"
      children:
        - id: "1.1"
          function: "translate_binary"
          wall_time_ms: 7100
          type: "function_call"
          children:
            - id: "1.1.1"
              function: "tikal_extract"
              service: "tikal"   # cross-service: code traced into submodule
              wall_time_ms: 2800
              type: "http_call"
              http_round_trips: 1
            - id: "1.1.2"
              function: "mt_translate"
              service: "mt-engine"
              wall_time_ms: 3500
              type: "http_call"
              http_round_trips: 13
  bottleneck_classification: "I/O-Network"
  bottleneck_detail: "13 sequential HTTP calls to MT service (3500ms)"
  top_bottlenecks:
    - step: "1.1.2", type: "I/O-Network", share: 48%
    - step: "1.1.1", type: "I/O-Network", share: 38%

Phase 5: Report

Report Structure

profile_result:
  entry_point_info:
    type: <string>                     # "api_endpoint" | "function" | "pipeline"
    location: <string>                 # file:line
    route: <string|null>               # API route (if endpoint)
    function: <string>                 # Entry point function name
  performance_map: <object>            # Full map from Phase 4
  bottleneck_classification: <string>  # Primary bottleneck type
  bottleneck_detail: <string>          # Human-readable description
  top_bottlenecks:
    - step, type, share, description
  optimization_hints:                  # CONFIRMED suspicions only (Phase 2)
    - hint with evidence
  suspicion_stack:                     # Full audit trail (confirmed + dismissed)
    - category: <string>
      location: <string>
      description: <string>
      verdict: <string>               # "confirmed" | "dismissed"
      evidence: <string>
      verification_note: <string>
  e2e_test:
    command: <string|null>             # E2E safety test command (from Phase 0)
    source: <string>                   # user / route / function / module / none
  instrumented_files: [<string>]       # Files with active instrumentation (empty if non-invasive only)
  wrong_tool_indicators: []            # Empty = proceed, non-empty = exit

Wrong Tool Indicators

Error Handling

References

• bottleneck_classification.md — classification taxonomy
• latency_estimation.md — latency heuristics (fallback for static-only mode)
• references/ci_tool_detection.md — stack/tool detection
• references/benchmark_generation.md — benchmark templates per stack

Runtime Summary Artifact

MANDATORY READ: Load references/coordinator_summary_contract.md

Emit an optimization-worker summary envelope.

Managed mode:

• ln-810 passes deterministic runId and exact summaryArtifactPath
• write the summary to the provided summaryArtifactPath

Standalone mode:

• omit runId and summaryArtifactPath
• write .hex-skills/runtime-artifacts/runs/{run_id}/optimization-worker/ln-811--{identifier}.json

Definition of Done

• Test command discovered or created for optimization target
• E2E safety test discovered (or documented as unavailable)
• Baseline measured: wall time, CPU, memory (3 runs, median)
• Call graph traced and function bodies read
• Suspicion stack built: each suspicion verified and mapped to instrumentation point
• Deep profile completed (non-invasive preferred, invasive if needed)
• Instrumented files reported (cleanup deferred to executor)
• Performance map built in standardized format (real measurements)
• Top 3 bottlenecks identified from measured data
• Wrong tool indicators evaluated from real metrics
• optimization_hints contain only CONFIRMED suspicions with measurement evidence
• Report prepared with measured findings
• Optimization profile artifact written to the shared location

Version: 3.0.0 Last Updated: 2026-03-15