Phase 14 v1: Pointer-Chase Reduction (tcache) NEUTRAL (+0.20%)

Implementation:
- Intrusive LIFO tcache layer (L1) before UnifiedCache
- TLS per-class bins (head pointer + count)
- Intrusive next pointers (via tiny_next_store/load SSOT)
- Cap: 64 blocks per class (default)
- ENV: HAKMEM_TINY_TCACHE=0/1 (default: 0, OFF)

A/B Test Results (Mixed 10-run):
- Baseline (TCACHE=0): 51,083,379 ops/s
- Optimized (TCACHE=1): 51,186,838 ops/s
- Mean delta: +0.20% (below +1.0% GO threshold)
- Median delta: +0.59%

Verdict: NEUTRAL - Freeze as research box (default OFF)

Root Cause (v1 wiring incomplete):
- Free side pushes to tcache via unified_cache_push()
- Alloc hot path (tiny_hot_alloc_fast) doesn't consume tcache
- tcache becomes "sink" without alloc-side pop → ROI not measurable

Files:
- Created: core/box/tiny_tcache_{env_box,box}.h, tiny_tcache_env_box.c
- Modified: core/front/tiny_unified_cache.h (integration)
- Modified: core/bench_profile.h (refresh sync)
- Modified: Makefile (build integration)
- Results: docs/analysis/PHASE14_POINTER_CHASE_REDUCTION_1_AB_TEST_RESULTS.md
- v2 Instructions: docs/analysis/PHASE14_POINTER_CHASE_REDUCTION_2_NEXT_INSTRUCTIONS.md

Next: Phase 14 v2 (connect tcache to tiny_front_hot_box alloc/free hot path)

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

core/box/tiny_tcache_env_box.c

@@ -0,0 +1,68 @@
+// ============================================================================
+// Phase 14 v1: Tiny tcache ENV Box (L0) - Implementation
+// ============================================================================
+
+#include "tiny_tcache_env_box.h"
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <unistd.h>
+
+// ============================================================================
+// Global State
+// ============================================================================
+
+_Atomic int g_tiny_tcache_enabled = -1;
+_Atomic uint16_t g_tiny_tcache_cap = 0;
+
+// ============================================================================
+// Init (Cold Path)
+// ============================================================================
+
+int tiny_tcache_env_init(void) {
+    const char* env_enabled = getenv("HAKMEM_TINY_TCACHE");
+    const char* env_cap = getenv("HAKMEM_TINY_TCACHE_CAP");
+
+    int enabled = 0;  // default: OFF (opt-in)
+    uint16_t cap = 64;  // default: 64 (glibc tcache-like)
+
+    // Parse HAKMEM_TINY_TCACHE
+    if (env_enabled && (env_enabled[0] == '1' || strcmp(env_enabled, "true") == 0 || strcmp(env_enabled, "TRUE") == 0)) {
+        enabled = 1;
+    }
+
+    // Parse HAKMEM_TINY_TCACHE_CAP
+    if (env_cap && *env_cap) {
+        int parsed = atoi(env_cap);
+        if (parsed > 0 && parsed <= 65535) {
+            cap = (uint16_t)parsed;
+        }
+    }
+
+    // Cache results
+    atomic_store_explicit(&g_tiny_tcache_enabled, enabled, memory_order_relaxed);
+    atomic_store_explicit(&g_tiny_tcache_cap, cap, memory_order_relaxed);
+
+    // Log once (stderr for immediate visibility)
+    if (enabled) {
+        char msg[128];
+        int n = snprintf(msg, sizeof(msg), "[TINY_TCACHE] enabled (cap=%u)\n", (unsigned)cap);
+        if (n > 0 && n < (int)sizeof(msg)) {
+            ssize_t w = write(2, msg, (size_t)n);
+            (void)w;
+        }
+    }
+
+    return enabled;
+}
+
+// ============================================================================
+// Refresh (Cold Path, called from bench_profile)
+// ============================================================================
+
+void tiny_tcache_env_refresh_from_env(void) {
+    // Reset to uninitialized state (-1 / 0)
+    // Next call to tiny_tcache_enabled() / tiny_tcache_cap() will re-read ENV
+    atomic_store_explicit(&g_tiny_tcache_enabled, -1, memory_order_relaxed);
+    atomic_store_explicit(&g_tiny_tcache_cap, 0, memory_order_relaxed);
+}