feat: Add ACE allocation failure tracing and debug hooks
This commit introduces a comprehensive tracing mechanism for allocation failures within the Adaptive Cache Engine (ACE) component. This feature allows for precise identification of the root cause for Out-Of-Memory (OOM) issues related to ACE allocations. Key changes include: - **ACE Tracing Implementation**: - Added environment variable to enable/disable detailed logging of allocation failures. - Instrumented , , and to distinguish between "Threshold" (size class mismatch), "Exhaustion" (pool depletion), and "MapFail" (OS memory allocation failure). - **Build System Fixes**: - Corrected to ensure is properly linked into , resolving an error. - **LD_PRELOAD Wrapper Adjustments**: - Investigated and understood the wrapper's behavior under , particularly its interaction with and checks. - Enabled debugging flags for environment to prevent unintended fallbacks to 's for non-tiny allocations, allowing comprehensive testing of the allocator. - **Debugging & Verification**: - Introduced temporary verbose logging to pinpoint execution flow issues within interception and routing. These temporary logs have been removed. - Created to facilitate testing of the tracing features. This feature will significantly aid in diagnosing and resolving allocation-related OOM issues in by providing clear insights into the failure pathways.
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Moe Charm (CI)
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PHASE8_VISUAL_SUMMARY.md
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PHASE8_VISUAL_SUMMARY.md
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# Phase 8 Comprehensive Benchmark - Visual Summary
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## Performance Comparison Charts
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### Working Set 256 (Hot Cache) - Bar Chart
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```
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HAKMEM ████████████████████████████████████████ 79.2 M ops/s (1.00x)
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System ███████████████████████████████████████████ 86.7 M ops/s (1.09x) ↑ 9%
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mimalloc ██████████████████████████████████████████████████████████ 114.9 M ops/s (1.45x) ↑ 45%
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```
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### Working Set 8192 (Realistic Workload) - Bar Chart
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```
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HAKMEM ████ 16.5 M ops/s (1.00x)
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System ██████████████ 57.1 M ops/s (3.46x) ↑ 246%
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mimalloc ████████████████████████ 96.5 M ops/s (5.85x) ↑ 485%
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```
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## Scalability Comparison
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### Performance Degradation (WS256 → WS8192)
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```
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mimalloc ████ 1.19x degradation [EXCELLENT]
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System ██████ 1.52x degradation [GOOD]
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HAKMEM ███████████████████ 4.80x degradation [CRITICAL ISSUE]
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```
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## Performance Gap Analysis
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### Cycle Budget (Estimated at 3.5 GHz)
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| Allocator | Cycles/Op | Extra Cycles vs Best |
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|-----------|-----------|---------------------|
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| mimalloc | 36 | 0 (baseline) |
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| System | 61 | +25 (+69%) |
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| HAKMEM | 212 | +176 (+489%) |
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**HAKMEM uses 176 extra cycles per operation compared to mimalloc!**
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### Where Are The Cycles Going?
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```
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Estimated cycle breakdown for HAKMEM WS8192:
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SuperSlab Lookup: ████████████████ 50-80 cycles
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Legacy Fallback: ██████████████ 30-50 cycles (when triggered)
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Fragmentation: ███████████ 30-50 cycles
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TLS Drain Logic: ███ 10-15 cycles
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Actual Work: ████████ 30-40 cycles
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─────────────────────────
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Total: ~212 cycles/operation
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mimalloc for comparison:
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Optimized Fast Path: ████████ 36 cycles total
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```
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## Priority Ranking
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### Critical Issues (Must Fix)
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```
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1. SuperSlab Scaling Priority: CRITICAL Impact: 246% perf loss
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└─ 4.8x degradation vs 1.5x for System malloc
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└─ "shared_fail→legacy" messages indicate capacity issues
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2. Fragmentation Priority: HIGH Impact: 30-50 cycles/op
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└─ SuperSlab list becomes inefficient at scale
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3. TLB Pressure Priority: HIGH Impact: Unknown, likely high
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└─ Many 512KB SuperSlabs → TLB misses
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```
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### Important Issues (Should Fix)
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```
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4. TLS Drain Overhead Priority: MEDIUM Impact: 9.4% on hot cache
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└─ Affects even best-case performance
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5. Fast Path Efficiency Priority: MEDIUM Impact: 9.4% on hot cache
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└─ Need more aggressive inlining
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```
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### Nice-to-Have
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```
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6. Metadata Optimization Priority: LOW Impact: Unknown
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└─ Reduce cache pollution from slab metadata
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```
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## Competitive Position
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### Current Status: Phase 8
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```
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Tier 1 (Production-Ready):
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mimalloc ████████████████████████ 96.5 M ops/s
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System ██████████████ 57.1 M ops/s
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Tier 2 (Needs Work):
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(empty)
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Tier 3 (Experimental):
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HAKMEM ████ 16.5 M ops/s ← YOU ARE HERE
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```
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### Target for Phase 12 (6 months)
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```
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Tier 1 (Production-Ready):
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mimalloc ████████████████████████ 96.5 M ops/s
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HAKMEM ████████████████████ 80+ M ops/s ← TARGET
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System ██████████████ 57.1 M ops/s
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Goal: Match or exceed System malloc, get within 20% of mimalloc
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```
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## Decision Matrix for Phase 9
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### Option A: Fix SuperSlab Architecture (Recommended)
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**Pros**:
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- Preserve existing work
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- Targeted fixes may yield big gains
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- Debug logs provide clear direction
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**Cons**:
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- May be fundamentally flawed architecture
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- Risk of incremental fixes not solving core issue
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**Time estimate**: 2-3 weeks
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**Success probability**: 60%
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### Option B: Hybrid Architecture
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**Pros**:
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- Keep TLS fast path (working well)
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- Replace SuperSlab backend with proven design
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- Best of both worlds
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**Cons**:
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- Major refactoring required
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- Lose SuperSlab work
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- Integration complexity
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**Time estimate**: 4-6 weeks
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**Success probability**: 75%
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### Option C: Start Over (Not Recommended Yet)
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**Pros**:
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- Clean slate
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- Can copy proven designs (mimalloc, jemalloc)
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**Cons**:
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- Lose all current work
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- No learning from mistakes
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- 3+ months delay
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**Time estimate**: 3-4 months
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**Success probability**: 85% (but high cost)
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## Recommended Path Forward
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### Phase 9: SuperSlab Deep Dive (2 weeks)
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**Week 1: Investigation**
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- Add comprehensive profiling
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- Measure cache/TLB misses
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- Analyze fragmentation patterns
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- Understand "shared_fail→legacy" root cause
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**Week 2: Targeted Fixes**
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- Implement hash table for SuperSlab lookup
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- Experiment with larger SuperSlabs (1-2MB)
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- Optimize fragmentation handling
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- Add better capacity management
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**Success criteria**:
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- WS8192: 16.5 → 35+ M ops/s (2x improvement)
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- Understand root cause even if fix incomplete
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### Phase 10: Decision Point
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**If Phase 9 successful (>35 M ops/s)**:
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- Continue with SuperSlab optimizations
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- Focus on fast path improvements
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- Target: 50 M ops/s by Phase 12
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**If Phase 9 unsuccessful (<30 M ops/s)**:
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- Switch to Hybrid Architecture (Option B)
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- Keep TLS layer, replace backend
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- Target: 60 M ops/s by Phase 14
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## Key Metrics to Track
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### Performance Metrics
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- [ ] WS256 throughput (target: 85+ M ops/s)
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- [ ] WS8192 throughput (target: 35+ M ops/s)
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- [ ] Degradation ratio (target: <2.5x)
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### Architecture Metrics
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- [ ] SuperSlab lookup latency (target: <20 cycles)
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- [ ] Cache miss rate (target: <5%)
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- [ ] TLB miss rate (target: <1%)
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- [ ] Fragmentation ratio (target: <20%)
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### Debug Metrics
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- [ ] "shared_fail→legacy" events (target: 0)
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- [ ] TLS_SLL_HDR_RESET events (target: 0)
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- [ ] Average SuperSlab count (target: <10 at WS8192)
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## Conclusion
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**Phase 8 Status**: COMPLETE
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- ✓ Comprehensive benchmarks executed
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- ✓ Statistical analysis completed
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- ✓ Root cause hypotheses identified
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- ✓ Clear path forward defined
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**Phase 9 Ready**: YES
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- Clear investigation targets
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- Specific metrics to measure
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- Decision criteria established
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**Confidence Level**: HIGH
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- Data is robust (low variance)
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- Gaps are well-understood
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- Multiple viable paths forward
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---
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**Next Action**: Begin Phase 9 - SuperSlab Deep Dive and Profiling
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**Timeline**:
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- Phase 9: 2 weeks (investigation + targeted fixes)
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- Phase 10: 1 week (decision point + planning)
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- Phase 11-12: 3-4 weeks (major optimizations)
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- Target completion: 6-8 weeks to production-ready
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**Risk Level**: MEDIUM
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- SuperSlab may be unfixable → fallback to Hybrid (Option B)
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- Hybrid adds 2-3 weeks but higher success probability
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- Total timeline stays within 10 weeks worst case
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