hakmem/core/box/free_path_stats_box.h

#ifndef HAKMEM_FREE_PATH_STATS_BOX_H
#define HAKMEM_FREE_PATH_STATS_BOX_H

#include <stdint.h>
#include <stdbool.h>
#include <stdlib.h>

typedef struct FreePathStats {
    uint64_t total_calls;

    uint64_t c7_ultra_fast;
    uint64_t c6_ultra_free_fast;   // Phase 4-2: C6 ULTRA-free
    uint64_t c6_ultra_alloc_hit;   // Phase 4-4: C6 ULTRA-alloc (TLS pop)
    uint64_t c6_ifl_push;          // Phase TLS-UNIFY-3: C6 intrusive push
    uint64_t c6_ifl_pop;           // Phase TLS-UNIFY-3: C6 intrusive pop
    uint64_t c6_ifl_fallback;      // Phase TLS-UNIFY-3: C6 intrusive fallback (slow)
    uint64_t c5_ultra_free_fast;   // Phase 5-1: C5 ULTRA-free
    uint64_t c5_ultra_alloc_hit;   // Phase 5-2: C5 ULTRA-alloc (TLS pop)
    uint64_t c4_ultra_free_fast;   // Phase 6: C4 ULTRA-free (cap=64)
    uint64_t c4_ultra_alloc_hit;   // Phase 6: C4 ULTRA-alloc (TLS pop)
    uint64_t smallheap_v3_fast;
    uint64_t smallheap_v6_fast;
    uint64_t smallheap_v7_fast;    // Phase v7-2: SmallHeap v7 fast free
    uint64_t tiny_heap_v1_fast;
    uint64_t pool_v1_fast;
    uint64_t remote_free;
    uint64_t super_lookup_called;
    uint64_t legacy_fallback;

    // Phase 4-1: Legacy per-class breakdown
    uint64_t legacy_by_class[8];  // C0-C7 の Legacy fallback 内訳

    // Phase POLICY-FAST-PATH-V2: Fast-path policy skip
    uint64_t policy_fast_v2_skip;  // Phase POLICY-FAST-PATH-V2 fast-path skips
} FreePathStats;

// ENV gate
static inline bool free_path_stats_enabled(void) {
    static int g_enabled = -1;     // -1: unknown, 0: off, 1: on
    static int g_probe_left = 64;  // tolerate early getenv() instability (bench_profile putenv)

    if (__builtin_expect(g_enabled == 1, 1)) return true;
    if (__builtin_expect(g_enabled == 0, 1)) return false;

    const char* e = getenv("HAKMEM_FREE_PATH_STATS");
    if (e && *e) {
        g_enabled = (*e != '0') ? 1 : 0;
        return g_enabled == 1;
    }

    if (g_probe_left-- > 0) {
        return false;  // keep g_enabled==-1, retry later
    }

    g_enabled = 0;
    return false;
}

// Global stats instance
extern FreePathStats g_free_path_stats;

// Increment macros (with unlikely guard)
#define FREE_PATH_STAT_INC(field) \
    do { if (__builtin_expect(free_path_stats_enabled(), 0)) { \
        g_free_path_stats.field++; \
    } } while(0)

#endif // HAKMEM_FREE_PATH_STATS_BOX_H