hakmem/core/hakmem_learn_log.c

#include "hakmem_learn_log.h"
#include <pthread.h>
#include <time.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

// Global registry of rings (simple, guarded by a mutex)
static hkm_log_ring_t* g_rings[256];
static int g_ring_count = 0;
static pthread_mutex_t g_ring_mu = PTHREAD_MUTEX_INITIALIZER;

// TLS ring and RNG state
static __thread hkm_log_ring_t* t_ring = NULL;
static __thread uint32_t t_rng = 0x12345678u;
static int g_sample_exp = 0; // exponent: 0=every, 8=1/256
static int g_inited = 0;

static inline uint64_t now_ns(void) {
    struct timespec ts; clock_gettime(CLOCK_REALTIME, &ts);
    return (uint64_t)ts.tv_sec*1000000000ull + (uint64_t)ts.tv_nsec;
}

static inline uint32_t tid_low(void) {
    return (uint32_t)(uintptr_t)pthread_self();
}

void hkm_log_init_tls(void) {
    if (g_inited == 0) {
        const char* s = getenv("HAKMEM_LEARN_SAMPLE");
        if (s) { int v = atoi(s); if (v>=0 && v<=16) g_sample_exp = v; }
        g_inited = 1;
    }
    if (!t_ring) {
        t_ring = (hkm_log_ring_t*)calloc(1, sizeof(hkm_log_ring_t));
        if (!t_ring) return;
        pthread_mutex_lock(&g_ring_mu);
        if (g_ring_count < 256) g_rings[g_ring_count++] = t_ring;
        pthread_mutex_unlock(&g_ring_mu);
        // seed rng with tid
        t_rng ^= tid_low();
    }
}

void hkm_log_maybe(uintptr_t site, uint32_t size, uint16_t class_idx) {
    if (!t_ring) hkm_log_init_tls();
    if (!t_ring) return;
    // 1/2^k sampling via LFSR-like xorshift
    t_rng ^= t_rng << 13; t_rng ^= t_rng >> 17; t_rng ^= t_rng << 5;
    if ((t_rng & ((1u<<g_sample_exp)-1u)) != 0u) return;
    uint32_t h = t_ring->head;
    hkm_log_entry_t* e = &t_ring->entries[h & 1023u];
    e->ts_ns = now_ns();
    e->site = site;
    e->size = size;
    e->class_idx = class_idx;
    e->tid_low = tid_low();
    // publish
    __atomic_store_n(&t_ring->head, h+1, __ATOMIC_RELEASE);
}

void hkm_log_flush_file(const char* path) {
    if (!path || !*path) return;
    FILE* fp = fopen(path, "a");
    if (!fp) return;
    pthread_mutex_lock(&g_ring_mu);
    for (int i=0;i<g_ring_count;i++) {
        hkm_log_ring_t* r = g_rings[i];
        if (!r) continue;
        // snapshot
        uint32_t head = __atomic_load_n(&r->head, __ATOMIC_ACQUIRE);
        uint32_t tail = r->tail;
        while (tail < head) {
            hkm_log_entry_t* e = &r->entries[tail & 1023u];
            fprintf(fp, "%llu,%p,%u,%u,%u\n",
                (unsigned long long)e->ts_ns, (void*)e->site, e->size, (unsigned)e->class_idx, e->tid_low);
            tail++;
        }
        r->tail = tail;
    }
    pthread_mutex_unlock(&g_ring_mu);
    fclose(fp);
}