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f95448c767
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CRITICAL DISCOVERY: Phase 9 LRU architecturally unreachable due to TLS SLL
Root Cause:
- TLS SLL fast path (95-99% of frees) does NOT decrement meta->used
- Slabs never appear empty (meta->used never reaches 0)
- superslab_free() never called
- hak_ss_lru_push() never called
- LRU cache utilization: 0% (should be >90%)
Impact:
- mmap/munmap churn: 6,455 syscalls (74.8% time)
- Performance: -94% regression (9.38M → 563K ops/s)
- Phase 9 design goal: FAILED (lazy deallocation non-functional)
Evidence:
- 200K iterations: [LRU_PUSH]=0, [LRU_POP]=877 misses
- Experimental verification with debug logs confirms theory
Solution: Option B - Periodic TLS SLL Drain
- Every 1,024 frees: drain TLS SLL → slab freelist
- Decrement meta->used properly → enable empty detection
- Expected: -96% syscalls, +1,300-1,700% throughput
Files:
- PHASE9_LRU_ARCHITECTURE_ISSUE.md: Comprehensive analysis (300+ lines)
- Includes design options A/B/C/D with tradeoff analysis
Next: Await ultrathink approval to implement Option B
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2025-11-14 06:49:32 +09:00 |
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