ef8e2ab9b5
Phase 59b: Speed-first Mode Baseline Rebase - Rebase on MIXED_TINYV3_C7_SAFE profile (Speed-first, no prewarm suppression) - hakmem: 58.478 M ops/s (CV 2.52%) - mimalloc: 120.979 M ops/s (CV 0.90%) - Ratio: 48.34% of mimalloc (down from 49.13% Balanced mode in Phase 59) - Reason for difference: Profile selection (Speed-first vs Balanced) and mimalloc environment variance - Status: COMPLETE (measurement-only, zero code changes) Phase 61: C7 ULTRA Header-Light Optimization Attempt - Objective: Skip header write on C7 ULTRA alloc hit (write only on refill) - Implementation: ENV gate HAKMEM_TINY_C7_ULTRA_HEADER_LIGHT (default OFF) - Result: +0.31% (NEUTRAL, below +1.0% GO threshold) - Baseline: 59.543 M ops/s (CV 1.53%) - Treatment: 59.729 M ops/s (CV 2.66%) - Root cause analysis: - tiny_region_id_write_header only 2.32% of time (lower than Phase 42 estimate 4.56%) - Header-light mode adds branch to hot path, negating write savings - Mixed workload dilutes C7-specific optimization effectiveness - Variance increased due to branch prediction variability - Decision: Kept as research box with ENV gate (default OFF) - Lesson: Workload-specific optimizations need careful verification with full workloads Updated Documentation: - PHASE59B_SPEED_FIRST_REBASE_RESULTS.md: Full measurement results and analysis - PHASE61_C7_ULTRA_HEADER_LIGHT_RESULTS.md: A/B test results and root cause analysis - PHASE61_C7_ULTRA_HEADER_LIGHT_IMPLEMENTATION.md: Implementation details and design - CURRENT_TASK.md: Updated status and next phase planning (Phase 62) - PERFORMANCE_TARGETS_SCORECARD.md: Updated baseline and M1 milestone status M1 (50%) Milestone Status: - Current: 48.34% (Speed-first profile) - Gap: -1.66% (within measurement noise) - Profile recommendation: Speed-first as canonical default for throughput focus 🤖 Generated with Claude Code Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
115 lines
2.7 KiB
Markdown
115 lines
2.7 KiB
Markdown
# Phase 59b: Speed-first Rebase Results
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**Date**: 2025-12-17
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**Objective**: Measure baseline with Speed-first mode (HAKMEM_PROFILE=MIXED_TINYV3_C7_SAFE) and update baseline ratio.
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---
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## Background
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Phase 59 used Balanced mode, but Phase 57's 60-minute soak test showed Speed-first mode wins across all metrics:
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- Throughput: Speed-first is higher (not -3.0% as previously recorded)
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- CV: Speed-first 1.58% < Balanced 5.38%
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- Tail p99: Speed-first 19.14 ns/op < Balanced 20.78 ns/op
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This phase re-measures baseline with Speed-first as the canonical configuration.
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---
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## Build Configuration
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```bash
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make clean
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make bench_random_mixed_hakmem_minimal
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make bench_random_mixed_mi
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```
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**Profile**: MIXED_TINYV3_C7_SAFE (Speed-first)
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---
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## Results
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### HAKMEM (Speed-first, 10 runs)
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```
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Run 1: 59703498 ops/s
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Run 2: 58304610 ops/s
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Run 3: 57661940 ops/s
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Run 4: 58971883 ops/s
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Run 5: 54922424 ops/s
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Run 6: 58840032 ops/s
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Run 7: 59513137 ops/s
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Run 8: 57656603 ops/s
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Run 9: 59560261 ops/s
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Run 10: 59641284 ops/s
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```
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**Statistics**:
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- Mean: 58,477,567 ops/s
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- Median: 58,876,007 ops/s
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- Min: 54,922,424 ops/s
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- Max: 59,703,498 ops/s
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- CV: 2.52%
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### mimalloc (10 runs)
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```
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Run 1: 121727781 ops/s
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Run 2: 122378721 ops/s
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Run 3: 120826927 ops/s
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Run 4: 119288198 ops/s
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Run 5: 121275784 ops/s
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Run 6: 119825073 ops/s
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Run 7: 120096029 ops/s
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Run 8: 121769295 ops/s
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Run 9: 120555258 ops/s
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Run 10: 122051669 ops/s
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```
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**Statistics**:
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- Mean: 120,979,474 ops/s
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- Median: 120,966,493 ops/s
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- Min: 119,288,198 ops/s
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- Max: 122,378,721 ops/s
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- CV: 0.90%
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---
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## Ratio Calculation
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**HAKMEM / mimalloc**: 58,477,567 / 120,979,474 = **48.34%**
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### Comparison with Phase 59
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| Metric | Phase 59 (Balanced) | Phase 59b (Speed-first) | Delta |
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|--------|---------------------|-------------------------|-------|
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| HAKMEM Mean | 58,476,000 ops/s | 58,477,567 ops/s | +0.00% |
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| mimalloc Mean | 119,086,000 ops/s | 120,979,474 ops/s | +1.59% |
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| Ratio | 49.13% | 48.34% | -0.79pp |
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**Note**: Speed-first mode shows slightly lower ratio (-0.79pp) due to mimalloc improvement (+1.59%), not HAKMEM regression. HAKMEM throughput is identical.
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---
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## Conclusion
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**Status**: COMPLETED
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**Findings**:
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1. Speed-first mode is the correct baseline (lower CV, better tail latency)
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2. New baseline ratio: **48.34%** (down 0.79pp from Phase 59 due to mimalloc variation)
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3. HAKMEM throughput remains stable at ~58.5M ops/s
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**Recommendation**:
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- Adopt Speed-first (MIXED_TINYV3_C7_SAFE) as canonical default
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- Update PERFORMANCE_TARGETS_SCORECARD.md with new baseline
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- Use 48.34% as reference for future comparisons
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---
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## Next Steps
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- Phase 61: C7 ULTRA header-light optimization
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- Target: +1.0% improvement from header write elimination
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