Phase 12 SP-SLOT + Mid-Large P0 fix: Pool TLS debug logging & analysis

Phase 12 SP-SLOT Box (Complete):
- Per-slot state tracking (UNUSED/ACTIVE/EMPTY) for shared SuperSlabs
- 3-stage allocation: EMPTY reuse → UNUSED reuse → New SS
- Results: 877 → 72 SuperSlabs (-92%), 563K → 1.30M ops/s (+131%)
- Reports: PHASE12_SP_SLOT_BOX_IMPLEMENTATION_REPORT.md, CURRENT_TASK.md

Mid-Large P0 Analysis (2025-11-14):
- Root cause: Pool TLS disabled by default (build.sh:106 → POOL_TLS_PHASE1=0)
- Fix: POOL_TLS_PHASE1=1 build flag → 0.24M → 0.97M ops/s (+304%)
- Identified P0-2: futex bottleneck (67% syscall time) in pool_remote_push mutex
- Added debug logging: pool_tls.c (refill failures), pool_tls_arena.c (mmap/chunk failures)
- Reports: MID_LARGE_P0_FIX_REPORT_20251114.md, BOTTLENECK_ANALYSIS_REPORT_20251114.md

Next: Lock-free remote queue to reduce futex from 67% → <10%

Files modified:
- core/hakmem_shared_pool.c (SP-SLOT implementation)
- core/pool_tls.c (debug logging + stdatomic.h)
- core/pool_tls_arena.c (debug logging + stdio.h/errno.h/stdatomic.h)
- CURRENT_TASK.md (Phase 12 completion status)

🤖 Generated with Claude Code

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

core/pool_tls.c

@@ -4,6 +4,7 @@
 #include <stdbool.h>
 #include <sys/syscall.h>
 #include <unistd.h>
+#include <stdatomic.h>
 #include "pool_tls_registry.h"
 
 static inline pid_t gettid_cached(void){
@@ -115,7 +116,17 @@ void* pool_alloc(size_t size) {
     }
 
     // Cold path: refill
-    return pool_refill_and_alloc(class_idx);
+    void* refill_ret = pool_refill_and_alloc(class_idx);
+    if (!refill_ret) {
+        // DEBUG: Log refill failure
+        static _Atomic int refill_fail_count = 0;
+        int fail_num = atomic_fetch_add(&refill_fail_count, 1);
+        if (fail_num < 10) {
+            fprintf(stderr, "[POOL_TLS] pool_refill_and_alloc FAILED: class=%d, size=%zu\n",
+                    class_idx, POOL_CLASS_SIZES[class_idx]);
+        }
+    }
+    return refill_ret;
 }
 
 // Ultra-fast free (5-6 cycles)