hakmem/core/hakmem_tiny_sfc.c

// hakmem_tiny_sfc.c - Box 5-NEW: Super Front Cache (SFC) Implementation
// Purpose: Slow path (refill/spill/config/stats), not inline
// Fast path is in tiny_alloc_fast_sfc.inc.h (inline)

#include "tiny_alloc_fast_sfc.inc.h"
#include "hakmem_tiny.h"
#include "hakmem_tiny_config.h"
#include "hakmem_tiny_superslab.h"
#include "tiny_tls.h"
#include <stdlib.h>
#include <string.h>
#include <stdio.h>

// ============================================================================
// Box 5-NEW: TLS Variables (defined here, extern in header)
// ============================================================================

__thread void* g_sfc_head[TINY_NUM_CLASSES] = {NULL};
__thread uint32_t g_sfc_count[TINY_NUM_CLASSES] = {0};
uint32_t g_sfc_capacity[TINY_NUM_CLASSES] = {0};  // Non-TLS: shared read-only config

// ============================================================================
// Box 5-NEW: Statistics (compile-time gated)
// ============================================================================

#if HAKMEM_DEBUG_COUNTERS
sfc_stats_t g_sfc_stats[TINY_NUM_CLASSES] = {0};
#endif

// ============================================================================
// Box 5-NEW: Global Config (from ENV)
// ============================================================================

int g_sfc_enabled = 0;  // Default: OFF (A/B testing)

static int g_sfc_default_capacity = SFC_DEFAULT_CAPACITY;
static int g_sfc_default_refill = SFC_DEFAULT_REFILL_COUNT;
static int g_sfc_default_spill_thresh = SFC_DEFAULT_SPILL_THRESH;

// Per-class overrides (0 = use default)
static int g_sfc_capacity_override[TINY_NUM_CLASSES] = {0};
static int g_sfc_refill_override[TINY_NUM_CLASSES] = {0};

// ============================================================================
// Box 5-NEW: Initialization
// ============================================================================

void sfc_init(void) {
    // Parse ENV: HAKMEM_SFC_ENABLE
    const char* env_enable = getenv("HAKMEM_SFC_ENABLE");
    if (env_enable && *env_enable && *env_enable != '0') {
        g_sfc_enabled = 1;
    }

    if (!g_sfc_enabled) {
        // SFC disabled, skip initialization
        return;
    }

    // Parse ENV: HAKMEM_SFC_CAPACITY (default capacity for all classes)
    const char* env_cap = getenv("HAKMEM_SFC_CAPACITY");
    if (env_cap && *env_cap) {
        int cap = atoi(env_cap);
        if (cap >= SFC_MIN_CAPACITY && cap <= SFC_MAX_CAPACITY) {
            g_sfc_default_capacity = cap;
        }
    }

    // Parse ENV: HAKMEM_SFC_REFILL_COUNT (default refill for all classes)
    const char* env_refill = getenv("HAKMEM_SFC_REFILL_COUNT");
    if (env_refill && *env_refill) {
        int refill = atoi(env_refill);
        if (refill >= 8 && refill <= 256) {
            g_sfc_default_refill = refill;
        }
    }

    // Parse ENV: HAKMEM_SFC_CAPACITY_CLASS{0..7} (per-class capacity override)
    for (int cls = 0; cls < TINY_NUM_CLASSES; cls++) {
        char var[64];
        snprintf(var, sizeof(var), "HAKMEM_SFC_CAPACITY_CLASS%d", cls);
        const char* env_cls_cap = getenv(var);
        if (env_cls_cap && *env_cls_cap) {
            int cap = atoi(env_cls_cap);
            if (cap >= SFC_MIN_CAPACITY && cap <= SFC_MAX_CAPACITY) {
                g_sfc_capacity_override[cls] = cap;
            }
        }
    }

    // Parse ENV: HAKMEM_SFC_REFILL_COUNT_CLASS{0..7} (per-class refill override)
    for (int cls = 0; cls < TINY_NUM_CLASSES; cls++) {
        char var[64];
        snprintf(var, sizeof(var), "HAKMEM_SFC_REFILL_COUNT_CLASS%d", cls);
        const char* env_cls_refill = getenv(var);
        if (env_cls_refill && *env_cls_refill) {
            int refill = atoi(env_cls_refill);
            if (refill >= 8 && refill <= 256) {
                g_sfc_refill_override[cls] = refill;
            }
        }
    }

    // Initialize per-class capacities (use override or default)
    for (int cls = 0; cls < TINY_NUM_CLASSES; cls++) {
        if (g_sfc_capacity_override[cls] > 0) {
            g_sfc_capacity[cls] = g_sfc_capacity_override[cls];
        } else {
            g_sfc_capacity[cls] = g_sfc_default_capacity;
        }
    }

    // One-shot debug log
    static int debug_printed = 0;
    if (!debug_printed) {
        debug_printed = 1;
        const char* env_debug = getenv("HAKMEM_SFC_DEBUG");
        if (env_debug && *env_debug && *env_debug != '0') {
            fprintf(stderr, "[SFC] Initialized: enabled=%d, default_cap=%d, default_refill=%d\n",
                    g_sfc_enabled, g_sfc_default_capacity, g_sfc_default_refill);
            for (int cls = 0; cls < TINY_NUM_CLASSES; cls++) {
                if (g_sfc_capacity_override[cls] > 0 || g_sfc_refill_override[cls] > 0) {
                    fprintf(stderr, "[SFC] Class %d: cap=%u, refill_override=%d\n",
                            cls, g_sfc_capacity[cls], g_sfc_refill_override[cls]);
                }
            }
        }
    }

    // Ensure stats (if requested) are printed at process exit.
    // This is inexpensive and guarded inside sfc_shutdown by HAKMEM_SFC_STATS_DUMP.
    atexit(sfc_shutdown);
}

void sfc_shutdown(void) {
    // Optional: Print stats at exit
#if HAKMEM_DEBUG_COUNTERS
    const char* env_dump = getenv("HAKMEM_SFC_STATS_DUMP");
    if (env_dump && *env_dump && *env_dump != '0') {
        sfc_print_stats();
    }
#endif

    // No cleanup needed (TLS memory freed by OS)
}

// ============================================================================
// Box 5-NEW: Refill (Slow Path) - STUB (real logic in hakmem.c)
// ============================================================================

// Stub - real implementation is inline in hakmem.c malloc() to avoid LTO issues
// This is just a placeholder for future modular refactoring
int sfc_refill(int cls, int target_count) {
    if (cls < 0 || cls >= TINY_NUM_CLASSES) return 0;
    if (!g_sfc_enabled) return 0;
    (void)target_count;

#if HAKMEM_DEBUG_COUNTERS
    g_sfc_stats[cls].refill_calls++;
#endif

    return 0;  // Actual refill happens inline in hakmem.c
}

// ============================================================================
// Box 5-NEW: Spill (Slow Path) - STUB (real logic in hakmem.c)
// ============================================================================

// Stub - real implementation is inline in hakmem.c free() to avoid LTO issues
// This is just a placeholder for future modular refactoring
int sfc_spill(int cls, int spill_count) {
    if (cls < 0 || cls >= TINY_NUM_CLASSES) return 0;
    if (!g_sfc_enabled) return 0;
    (void)spill_count;

#if HAKMEM_DEBUG_COUNTERS
    g_sfc_stats[cls].spill_calls++;
#endif

    return 0;  // Actual spill happens inline in hakmem.c
}

// ============================================================================
// Box 5-NEW: Configuration API
// ============================================================================

sfc_config_t sfc_get_config(int cls) {
    sfc_config_t cfg = {0};

    if (cls >= 0 && cls < TINY_NUM_CLASSES) {
        cfg.capacity = g_sfc_capacity[cls];

        // Refill count (use override or default)
        cfg.refill_count = (g_sfc_refill_override[cls] > 0)
                           ? g_sfc_refill_override[cls]
                           : g_sfc_default_refill;

        cfg.spill_thresh = g_sfc_default_spill_thresh;
    }

    return cfg;
}

void sfc_set_config(int cls, sfc_config_t cfg) {
    if (cls < 0 || cls >= TINY_NUM_CLASSES) return;

    // Validate capacity
    if (cfg.capacity >= SFC_MIN_CAPACITY && cfg.capacity <= SFC_MAX_CAPACITY) {
        g_sfc_capacity[cls] = cfg.capacity;
    }

    // Validate refill count
    if (cfg.refill_count >= 8 && cfg.refill_count <= 256) {
        g_sfc_refill_override[cls] = cfg.refill_count;
    }

    // Spill threshold (future use)
    if (cfg.spill_thresh > 0 && cfg.spill_thresh <= 100) {
        // Currently unused
    }
}

// ============================================================================
// Box 5-NEW: Statistics API
// ============================================================================

#if HAKMEM_DEBUG_COUNTERS

sfc_stats_t sfc_get_stats(int cls) {
    sfc_stats_t stats = {0};

    if (cls >= 0 && cls < TINY_NUM_CLASSES) {
        stats = g_sfc_stats[cls];
    }

    return stats;
}

void sfc_reset_stats(int cls) {
    if (cls >= 0 && cls < TINY_NUM_CLASSES) {
        memset(&g_sfc_stats[cls], 0, sizeof(sfc_stats_t));
    }
}

void sfc_print_stats(void) {
    fprintf(stderr, "\n=== SFC Statistics (Box 5-NEW) ===\n");

    uint64_t total_alloc_hits = 0;
    uint64_t total_alloc_misses = 0;
    uint64_t total_refill_calls = 0;
    uint64_t total_refill_blocks = 0;

    for (int cls = 0; cls < TINY_NUM_CLASSES; cls++) {
        sfc_stats_t* s = &g_sfc_stats[cls];

        uint64_t total_allocs = s->alloc_hits + s->alloc_misses;
        if (total_allocs == 0) continue;  // Skip unused classes

        total_alloc_hits += s->alloc_hits;
        total_alloc_misses += s->alloc_misses;
        total_refill_calls += s->refill_calls;
        total_refill_blocks += s->refill_blocks;

        double hit_rate = (double)s->alloc_hits / total_allocs * 100.0;
        double refill_freq = (double)s->refill_calls / total_allocs * 100.0;

        fprintf(stderr, "Class %d (%3zu B): allocs=%llu, hit_rate=%.2f%%, "
                        "refills=%llu (%.4f%%), spills=%llu, cap=%u\n",
                cls, g_tiny_class_sizes[cls],
                (unsigned long long)total_allocs, hit_rate,
                (unsigned long long)s->refill_calls, refill_freq,
                (unsigned long long)s->spill_calls,
                g_sfc_capacity[cls]);
    }

    // Summary
    uint64_t grand_total = total_alloc_hits + total_alloc_misses;
    if (grand_total > 0) {
        double overall_hit_rate = (double)total_alloc_hits / grand_total * 100.0;
        double overall_refill_freq = (double)total_refill_calls / grand_total * 100.0;

        fprintf(stderr, "\n=== SFC Summary ===\n");
        fprintf(stderr, "Total allocs:    %llu\n", (unsigned long long)grand_total);
        fprintf(stderr, "Overall hit rate: %.2f%% (target: >95%%)\n", overall_hit_rate);
        fprintf(stderr, "Refill frequency: %.4f%% (target: <0.03%%)\n", overall_refill_freq);
        fprintf(stderr, "Refill calls:    %llu (target: <50K for 4M ops/s workload)\n",
                (unsigned long long)total_refill_calls);
        fprintf(stderr, "Refill blocks:   %llu (avg %.1f blocks/refill)\n",
                (unsigned long long)total_refill_blocks,
                total_refill_calls > 0 ? (double)total_refill_blocks / total_refill_calls : 0.0);

        // Check targets
        if (overall_hit_rate >= 95.0) {
            fprintf(stderr, "✅ Hit rate target achieved!\n");
        } else {
            fprintf(stderr, "⚠️  Hit rate below target (increase capacity?)\n");
        }

        if (overall_refill_freq < 0.03) {
            fprintf(stderr, "✅ Refill frequency target achieved (-98.5%% reduction)!\n");
        } else {
            fprintf(stderr, "⚠️  Refill frequency above target (increase refill_count?)\n");
        }
    }

    fprintf(stderr, "===========================\n\n");
}

#endif // HAKMEM_DEBUG_COUNTERS

// ============================================================================
// End of hakmem_tiny_sfc.c
// ============================================================================