Implemented C7 ULTRA allocation hotpath optimization attempt as per Phase 62A instructions.
Objective: Reduce dependency chain in tiny_c7_ultra_alloc() by:
1. Eliminating per-call tiny_front_v3_c7_ultra_header_light_enabled() checks
2. Using TLS headers_initialized flag set during refill
3. Reducing branch count and register pressure
Implementation:
- New ENV box: core/box/c7_ultra_alloc_depchain_opt_box.h
- HAKMEM_C7_ULTRA_ALLOC_DEPCHAIN_OPT=0/1 gate (default OFF)
- Modified tiny_c7_ultra_alloc() with optimized path
- Preserved original path for compatibility
Results (Mixed benchmark, 10-run):
- Baseline (OPT=0): 59.300 M ops/s (CV 1.98%)
- Treatment (OPT=1): 58.879 M ops/s (CV 1.83%)
- Delta: -0.71% (NEUTRAL, within ±1.0% threshold but negative)
- Status: NEUTRAL → Research box (default OFF)
Root Cause Analysis:
1. LTO optimization already inlines header_light function (call cost = 0)
2. TLS access (memory load + offset) not cheaper than function call
3. Layout tax from code addition (I-cache disruption pattern from Phases 43/46A/47)
4. 5.18% stack % is not optimizable hotspot (already well-optimized)
Key Lessons:
- LTO-optimized function calls can be cheaper than TLS field access
- Micro-optimizations on already-optimized paths show diminishing/negative returns
- 48.34% gap to mimalloc is likely algorithmic, not micro-architectural
- Layout tax remains consistent pattern across attempted micro-optimizations
Decision:
- NEUTRAL verdict → kept as research box with ENV gate (default OFF)
- Not adopted as production default
- Next phases: Option B (production readiness pivot) likely higher ROI than further micro-opts
Box Theory Compliance: ✅ Compliant (single point, reversible, clear boundary)
Performance Compliance: ❌ No (-0.71% regression)
Documentation:
- PHASE62A_C7_ULTRA_DEPCHAIN_OPT_RESULTS.md: Full A/B test analysis
- CURRENT_TASK.md: Updated with results and next phase options
🤖 Generated with Claude Code
Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
- Update environment profile presets and visibility analysis
- Enhance small object and tiny segment v4 box implementations
- Refine C7 ultra and C6 heavy allocation strategies
- Add comprehensive performance metrics and design documentation
🤖 Generated with Claude Code
Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>
