Phase 10: TLS/SFC aggressive cache tuning (syscall reduction failed)

Goal: Reduce backend transitions by increasing frontend hit rate
Result: +2% best case, syscalls unchanged (root cause: SuperSlab churn)

Implementation:

1. Cache capacity expansion (2-8x per-class)
   - Hot classes (C0-C3): 4x increase (512 slots)
   - Medium classes (C4-C6): 2-3x increase
   - Class 7 (1KB): 2x increase (128 slots)
   - Fast cache: 2x default capacity

2. Refill batch size increase (4-8x)
   - Global default: 16 → 64 (4x)
   - Hot classes: 128 (8x) via HAKMEM_TINY_REFILL_COUNT_HOT
   - Mid classes: 96 (6x) via HAKMEM_TINY_REFILL_COUNT_MID
   - Class 7: 64 → 128 (2x)
   - SFC refill: 64 → 128 (2x)

3. Adaptive sizing aggressive parameters
   - Grow threshold: 80% → 70% (expand earlier)
   - Shrink threshold: 20% → 10% (shrink less)
   - Growth rate: 2x → 1.5x (smoother growth)
   - Max capacity: 2048 → 4096 (2x ceiling)
   - Adapt frequency: Every 10 → 5 refills (more responsive)

Performance Results (100K iterations):

Before (Phase 9):
- Performance: 9.71M ops/s
- Syscalls: 1,729 (mmap:877, munmap:852)

After (Phase 10):
- Default settings: 8.77M ops/s (-9.7%) ⚠️
- Optimal ENV: 9.89M ops/s (+2%) ✅
- Syscalls: 1,729 (unchanged) ❌

Optimal ENV configuration:
export HAKMEM_TINY_REFILL_COUNT_HOT=256
export HAKMEM_TINY_REFILL_COUNT_MID=192

Root Cause Analysis:

Bottleneck is NOT TLS/SFC hit rate, but SuperSlab allocation churn:
- 877 SuperSlabs allocated (877MB via mmap)
- Phase 9 LRU cache not utilized (no frees during benchmark)
- All SuperSlabs retained until program exit
- System malloc: 9 syscalls vs HAKMEM: 1,729 syscalls (192x gap)

Conclusion:

TLS/SFC tuning cannot solve SuperSlab allocation policy problem.
Next step: Phase 11 SuperSlab Prewarm strategy to eliminate
mmap/munmap during benchmark execution.

ChatGPT review: Strategy validated, Option A (Prewarm) recommended.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

core/tiny_adaptive_sizing.c

@@ -59,7 +59,9 @@ void adaptive_sizing_init(void) {
 void grow_tls_cache(int class_idx) {
     TLSCacheStats* stats = &g_tls_cache_stats[class_idx];
 
-    size_t new_capacity = stats->capacity * 2;
+    // Phase 10: Aggressive growth - add 50% instead of doubling
+    // This allows more gradual growth to match actual demand
+    size_t new_capacity = stats->capacity + (stats->capacity / 2);
     if (new_capacity > TLS_CACHE_MAX_CAPACITY) {
         new_capacity = TLS_CACHE_MAX_CAPACITY;
     }
@@ -73,7 +75,7 @@ void grow_tls_cache(int class_idx) {
     stats->grow_count++;
 
     if (g_adaptive_logging_enabled) {
-        fprintf(stderr, "[TLS_CACHE] Grow class %d: %zu → %zu slots (grow_count=%zu)\n",
+        fprintf(stderr, "[TLS_CACHE] Grow class %d: %zu → %zu slots (+50%%, grow_count=%zu)\n",
                 class_idx, old_capacity, stats->capacity, stats->grow_count);
     }
 }