hakmem/core/box/front_metrics_box.c

// front_metrics_box.c - Box FrontMetrics Implementation
// Purpose: Collect and report frontend layer hit rates

#include "front_metrics_box.h"
#include "../hakmem_tiny_stats_api.h"
#include "../hakmem_stats_master.h"  // Phase 4d: Master stats control
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// ============================================================================
// Per-thread counters (NEW - declared in header, defined here)
// ============================================================================

__thread uint64_t g_front_ultrahot_hit[TINY_NUM_CLASSES] = {0};
__thread uint64_t g_front_ultrahot_miss[TINY_NUM_CLASSES] = {0};

__thread uint64_t g_front_heapv2_hit[TINY_NUM_CLASSES] = {0};
__thread uint64_t g_front_heapv2_miss[TINY_NUM_CLASSES] = {0};

__thread uint64_t g_front_class5_hit[TINY_NUM_CLASSES] = {0};
__thread uint64_t g_front_class5_miss[TINY_NUM_CLASSES] = {0};

// ============================================================================
// Existing counters (defined in hakmem_tiny.c, extern here for reading)
// ============================================================================

extern unsigned long long g_front_fc_hit[TINY_NUM_CLASSES];
extern unsigned long long g_front_fc_miss[TINY_NUM_CLASSES];
extern unsigned long long g_front_sfc_hit[TINY_NUM_CLASSES];
extern unsigned long long g_front_sll_hit[TINY_NUM_CLASSES];

// ============================================================================
// Enable flag (cached)
// ============================================================================

int front_metrics_enabled(void) {
    static int g_enabled = -1;
    if (__builtin_expect(g_enabled == -1, 0)) {
#if HAKMEM_BUILD_RELEASE
        g_enabled = 0;
#else
        const char* env = getenv("HAKMEM_TINY_FRONT_METRICS");
        g_enabled = (env && *env && *env != '0') ? 1 : 0;
#endif
    }
    return g_enabled;
}

// ============================================================================
// Dump frontend metrics (CSV format)
// ============================================================================

void hak_tiny_front_metrics_dump(void) {
    if (!front_metrics_enabled()) {
        return;
    }

#if !HAKMEM_BUILD_RELEASE
    if (!hak_stats_check("HAKMEM_TINY_FRONT_DUMP", "front")) {
        return;
    }
#endif

    fprintf(stderr, "\n========== Box FrontMetrics: Layer Hit Rates ==========\n");
    fprintf(stderr, "Purpose: Identify which frontend layers are doing real work\n");
    fprintf(stderr, "Legend: UH=UltraHot, HV2=HeapV2, C5=Class5, FC=FastCache, SFC=SuperFrontCache, SLL=TLS_SLL\n\n");

    fprintf(stderr, "%-5s %10s %10s %10s %10s %10s %10s %12s | %6s %6s %6s %6s %6s %6s\n",
            "Class", "UH_hit", "HV2_hit", "C5_hit", "FC_hit", "SFC_hit", "SLL_hit", "Total",
            "UH%", "HV2%", "C5%", "FC%", "SFC%", "SLL%");
    fprintf(stderr, "------|----------|----------|----------|----------|----------|----------|-------------|");
    fprintf(stderr, "-------|-------|-------|-------|-------|-------\n");

    for (int cls = 0; cls < TINY_NUM_CLASSES; cls++) {
        uint64_t uh_hit = g_front_ultrahot_hit[cls];
        uint64_t hv2_hit = g_front_heapv2_hit[cls];
        uint64_t c5_hit = g_front_class5_hit[cls];
        uint64_t fc_hit = g_front_fc_hit[cls];
        uint64_t sfc_hit = g_front_sfc_hit[cls];
        uint64_t sll_hit = g_front_sll_hit[cls];

        uint64_t total = uh_hit + hv2_hit + c5_hit + fc_hit + sfc_hit + sll_hit;

        if (total == 0) {
            fprintf(stderr, "C%-4d %10s %10s %10s %10s %10s %10s %12s | %6s %6s %6s %6s %6s %6s\n",
                    cls, "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-", "-");
            continue;
        }

        double uh_pct = (double)uh_hit / total * 100.0;
        double hv2_pct = (double)hv2_hit / total * 100.0;
        double c5_pct = (double)c5_hit / total * 100.0;
        double fc_pct = (double)fc_hit / total * 100.0;
        double sfc_pct = (double)sfc_hit / total * 100.0;
        double sll_pct = (double)sll_hit / total * 100.0;

        fprintf(stderr, "C%-4d %10lu %10lu %10lu %10lu %10lu %10lu %12lu | %5.1f%% %5.1f%% %5.1f%% %5.1f%% %5.1f%% %5.1f%%\n",
                cls,
                (unsigned long)uh_hit,
                (unsigned long)hv2_hit,
                (unsigned long)c5_hit,
                (unsigned long)fc_hit,
                (unsigned long)sfc_hit,
                (unsigned long)sll_hit,
                (unsigned long)total,
                uh_pct, hv2_pct, c5_pct, fc_pct, sfc_pct, sll_pct);
    }

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

    // Analysis recommendations
    fprintf(stderr, "Analysis Recommendations:\n");
    fprintf(stderr, "  - Layers with >80%% hit rate: Keep and optimize (hot path)\n");
    fprintf(stderr, "  - Layers with <5%% hit rate: Consider pruning (dead weight)\n");
    fprintf(stderr, "  - Multiple layers >20%%: Potential redundancy, test pruning\n\n");
}

// Register dump at shutdown
static void front_metrics_atexit(void) __attribute__((destructor));
static void front_metrics_atexit(void) {
    hak_tiny_front_metrics_dump();
}