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Phase 18 v2: BENCH_MINIMAL — NEUTRAL (+2.32% throughput, -5.06% instructions)
## Summary
Phase 18 v2 attempted instruction count reduction via conditional compilation:
- Stats collection → no-op
- ENV checks → constant propagation
- Binary size: 653K → 649K (-4K, -0.6%)
Result: NEUTRAL (below GO threshold)
- Throughput: +2.32% (target: +5% minimum) ❌
- Instructions: -5.06% (target: -15% minimum) ❌
- Cycles: -3.26% (positive signal)
- Branches: -8.67% (positive signal)
- Cache-misses: +30% (unexpected, likely layout)
## Analysis
Positive signals:
- Implementation correct (Branch -8.67%, Instruction -5.06%)
- Binary size reduced (-4K)
- Modest throughput gain (+2.32%)
- Cycles and branch overhead reduced
Negative signals:
- Instruction reduction insufficient (-5.06% << -15% smoking gun)
- Throughput gain below +5% threshold
- Cache-misses increased (+30%, layout noise?)
## Verdict
Freeze Phase 18 v2 (weak positive, insufficient for production).
Per user guidance: "If instructions don't drop clearly, continuation value is thin."
-5.06% instruction reduction is marginal. Allocator micro-optimization plateau confirmed.
## Key Insight
Phase 17 showed:
- IPC = 2.30 (consistent, memory-bound)
- I-cache gap: 55% (Phase 17: 153K → 68K)
- Instruction gap: 48% (Phase 17: 41.3B → 21.5B)
Phase 18 v1/v2 results confirm:
- Layout tweaks are fragile (v1: I-cache +91%)
- Instruction removal is modest benefit (v2: -5.06%)
- Allocator is NOT the bottleneck (IPC constant, memory-limited)
## Recommendation
Do NOT continue Phase 18 micro-optimizations.
Next frontier requires different approach:
1. Architectural redesign (SIMD, lock-free, batching)
2. Memory layout optimization (cache-friendly structures)
3. Broader profiling (not allocator-focused)
Or: Accept that 48M → 85M (75% gap) is achievable with current architecture.
Files:
- docs/analysis/PHASE18_HOT_TEXT_ISOLATION_2_AB_TEST_RESULTS.md (results)
- CURRENT_TASK.md (Phase 18 complete status)
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
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2025-12-15 06:02:28 +09:00 |
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