C++ STATS_LOCK函数代码示例

/* FIXME: Is it necessary to keep this copy/pasted code? */
void do_item_unlink_nolock(item *it, const uint32_t hv) {
    MEMCACHED_ITEM_UNLINK(ITEM_key(it), it->nkey, it->nbytes);
    if ((it->it_flags & ITEM_LINKED) != 0) {
        it->it_flags &= ~ITEM_LINKED;
        STATS_LOCK();
        stats.curr_bytes -= ITEM_ntotal(it);
        stats.curr_items -= 1;
        STATS_UNLOCK();
        assoc_delete(ITEM_key(it), it->nkey, hv);
        item_unlink_q(it);
        do_item_remove(it);
    }
}

void do_item_unlink(item *it) {
    MEMCACHED_ITEM_UNLINK(ITEM_key(it), it->nbytes);
    if ((it->it_flags & ITEM_LINKED) != 0) {
        it->it_flags &= ~ITEM_LINKED;
        STATS_LOCK();
        stats.curr_bytes -= ITEM_ntotal(it);
        stats.curr_items -= 1;
        STATS_UNLOCK();
        assoc_delete(ITEM_key(it), it->nkey);
        item_unlink_q(it);
        if (it->refcount == 0) item_free(it);
    }
}

void stats_prefix_record_get(const char *key, const size_t nkey, const bool is_hit) {
    PREFIX_STATS *pfs;

    STATS_LOCK();
    pfs = stats_prefix_find(key, nkey);
    if (NULL != pfs) {
        pfs->num_gets++;
        if (is_hit) {
            pfs->num_hits++;
        }
    }
    STATS_UNLOCK();
}

static void slab_rebalance_finish(void) {
    slabclass_t *s_cls;
    slabclass_t *d_cls;

    pthread_mutex_lock(&cache_lock);
    pthread_mutex_lock(&slabs_lock);

    s_cls = &slabclass[slab_rebal.s_clsid];
    d_cls   = &slabclass[slab_rebal.d_clsid];

    /* At this point the stolen slab is completely clear */
    //相当于把指针赋NULL值
    s_cls->slab_list[s_cls->killing - 1] =
        s_cls->slab_list[s_cls->slabs - 1];
    s_cls->slabs--;//源slab class的内存页数减一 
    s_cls->killing = 0;
    
    //内存页所有字节清零，这个也很重要的 
    memset(slab_rebal.slab_start, 0, (size_t)settings.item_size_max);

    //将slab_rebal.slab_start指向的一个页内存馈赠给目标slab class  
    //slab_rebal.slab_start指向的页是从源slab class中得到的。
    d_cls->slab_list[d_cls->slabs++] = slab_rebal.slab_start;

    //按照目标slab class的item尺寸进行划分这个页，并且将这个页的  
    //内存并入到目标slab class的空闲item队列中  
    split_slab_page_into_freelist(slab_rebal.slab_start,
        slab_rebal.d_clsid);

    //清零
    slab_rebal.done       = 0;
    slab_rebal.s_clsid    = 0;
    slab_rebal.d_clsid    = 0;
    slab_rebal.slab_start = NULL;
    slab_rebal.slab_end   = NULL;
    slab_rebal.slab_pos   = NULL;

    slab_rebalance_signal = 0;//rebalance线程完成工作后，再次进入休眠状态

    pthread_mutex_unlock(&slabs_lock);
    pthread_mutex_unlock(&cache_lock);

    STATS_LOCK();
    stats.slab_reassign_running = false;
    stats.slabs_moved++;
    STATS_UNLOCK();

    if (settings.verbose > 1) {
        fprintf(stderr, "finished a slab move\n");
    }
}

static int slab_rebalance_start(void) {
    slabclass_t *s_cls;
    int no_go = 0;

    pthread_mutex_lock(&slabs_lock);

    if (slab_rebal.s_clsid < POWER_SMALLEST ||
        slab_rebal.s_clsid > power_largest  ||
        slab_rebal.d_clsid < SLAB_GLOBAL_PAGE_POOL ||
        slab_rebal.d_clsid > power_largest  ||
        slab_rebal.s_clsid == slab_rebal.d_clsid)
        no_go = -2;

    s_cls = &slabclass[slab_rebal.s_clsid];

    if (!grow_slab_list(slab_rebal.d_clsid)) {
        no_go = -1;
    }

    if (s_cls->slabs < 2)
        no_go = -3;

    if (no_go != 0) {
        pthread_mutex_unlock(&slabs_lock);
        return no_go; /* Should use a wrapper function... */
    }

    /* Always kill the first available slab page as it is most likely to
     * contain the oldest items
     */
    slab_rebal.slab_start = s_cls->slab_list[0];
    slab_rebal.slab_end   = (char *)slab_rebal.slab_start +
        (s_cls->size * s_cls->perslab);
    slab_rebal.slab_pos   = slab_rebal.slab_start;
    slab_rebal.done       = 0;

    /* Also tells do_item_get to search for items in this slab */
    slab_rebalance_signal = 2;

    if (settings.verbose > 1) {
        fprintf(stderr, "Started a slab rebalance\n");
    }

    pthread_mutex_unlock(&slabs_lock);

    STATS_LOCK();
    stats_state.slab_reassign_running = true;
    STATS_UNLOCK();

    return 0;
}

static void *lru_maintainer_thread(void *arg) {
    int i;
    useconds_t to_sleep = MIN_LRU_MAINTAINER_SLEEP;
    rel_time_t last_crawler_check = 0;
    struct crawler_expired_data cdata;
    memset(&cdata, 0, sizeof(struct crawler_expired_data));
    pthread_mutex_init(&cdata.lock, NULL);
    cdata.crawl_complete = true; // kick off the crawler.

    pthread_mutex_lock(&lru_maintainer_lock);
    if (settings.verbose > 2)
        fprintf(stderr, "Starting LRU maintainer background thread\n");
    while (do_run_lru_maintainer_thread) {
        int did_moves = 0;
        pthread_mutex_unlock(&lru_maintainer_lock);
        usleep(to_sleep);
        pthread_mutex_lock(&lru_maintainer_lock);

        STATS_LOCK();
        stats.lru_maintainer_juggles++;
        STATS_UNLOCK();
        /* We were asked to immediately wake up and poke a particular slab
         * class due to a low watermark being hit */
        if (lru_maintainer_check_clsid != 0) {
            did_moves = lru_maintainer_juggle(lru_maintainer_check_clsid);
            lru_maintainer_check_clsid = 0;
        } else {
            for (i = POWER_SMALLEST; i < MAX_NUMBER_OF_SLAB_CLASSES; i++) {
                did_moves += lru_maintainer_juggle(i);
            }
        }
        if (did_moves == 0) {
            if (to_sleep < MAX_LRU_MAINTAINER_SLEEP)
                to_sleep += 1000;
        } else {
            to_sleep /= 2;
            if (to_sleep < MIN_LRU_MAINTAINER_SLEEP)
                to_sleep = MIN_LRU_MAINTAINER_SLEEP;
        }
        /* Once per second at most */
        if (settings.lru_crawler && last_crawler_check != current_time) {
            lru_maintainer_crawler_check(&cdata);
            last_crawler_check = current_time;
        }
    }
    pthread_mutex_unlock(&lru_maintainer_lock);
    if (settings.verbose > 2)
        fprintf(stderr, "LRU maintainer thread stopping\n");

    return NULL;
}

static void *assoc_maintenance_thread(void *arg) {

    while (do_run_maintenance_thread) {
        int ii = 0;

        /* Lock the cache, and bulk move multiple buckets to the new
         * hash table. */
        mutex_lock(&cache_lock);

        for (ii = 0; ii < hash_bulk_move && expanding; ++ii) {
            item *it, *next;
            int bucket;

            for (it = old_hashtable[expand_bucket]; NULL != it; it = next) {
                next = it->h_next;

                bucket = hash(ITEM_key(it), it->nkey, 0) & hashmask(hashpower);
                it->h_next = primary_hashtable[bucket];
                primary_hashtable[bucket] = it;
            }

            old_hashtable[expand_bucket] = NULL;

            expand_bucket++;
            if (expand_bucket == hashsize(hashpower - 1)) {
                expanding = false;
                free(old_hashtable);
                STATS_LOCK();
                stats.hash_bytes -= hashsize(hashpower - 1) * sizeof(void *);
                stats.hash_is_expanding = 0;
                STATS_UNLOCK();
                if (settings.verbose > 1)
                    fprintf(stderr, "Hash table expansion done\n");
            }
        }

        if (!expanding) {
            // added by Bin:
            fprintf(stderr, "\nHash table expansion done\n");
            //assoc_pre_bench();
            //assoc_post_bench();

            /* We are done expanding.. just wait for next invocation */
            pthread_cond_wait(&maintenance_cond, &cache_lock);
        }

        pthread_mutex_unlock(&cache_lock);
    }
    return NULL;
}

static int slab_rebalance_start(void) {
    slabclass_t *s_cls;
    int no_go = 0;

    pthread_mutex_lock(&slabs_lock);

    if (slab_rebal.s_clsid < POWER_SMALLEST ||
        slab_rebal.s_clsid > power_largest  ||
        slab_rebal.d_clsid < POWER_SMALLEST ||
        slab_rebal.d_clsid > power_largest  ||
        slab_rebal.s_clsid == slab_rebal.d_clsid)
        no_go = -2;

    s_cls = &slabclass[slab_rebal.s_clsid];

    if (!grow_slab_list(slab_rebal.d_clsid)) {
        no_go = -1;
    }

    if (s_cls->slabs < 2)
        no_go = -3;

    if (no_go != 0) {
        pthread_mutex_unlock(&slabs_lock);
        return no_go; /* Should use a wrapper function... */
    }

    s_cls->killing = 1;

    slab_rebal.slab_start = s_cls->slab_list[s_cls->killing - 1];
    slab_rebal.slab_end   = (char *)slab_rebal.slab_start +
        (s_cls->size * s_cls->perslab);
    slab_rebal.slab_pos   = slab_rebal.slab_start;
    slab_rebal.done       = 0;

    /* Also tells do_item_get to search for items in this slab */
    slab_rebalance_signal = 2;

    if (settings.verbose > 1) {
        fprintf(stderr, "Started a slab rebalance\n");
    }

    pthread_mutex_unlock(&slabs_lock);

    STATS_LOCK();
    stats.slab_reassign_running = true;
    STATS_UNLOCK();

    return 0;
}

void assoc_init(const int hashtable_init) {
    if (hashtable_init) {
        hashpower = hashtable_init;
    }
    primary_hashtable = calloc(hashsize(hashpower), sizeof(void *));
    if (! primary_hashtable) {
        fprintf(stderr, "Failed to init hashtable.\n");
        exit(EXIT_FAILURE);
    }
    STATS_LOCK();
    stats.hash_power_level = hashpower;
    stats.hash_bytes = hashsize(hashpower) * sizeof(void *);
    STATS_UNLOCK();
}

/* FIXME: Is it necessary to keep this copy/pasted code? */
void do_item_unlink_nolock(item *it, const uint32_t hv) {
		syslog(LOG_INFO, "[%s:%s:%d]", __FILE__, __func__, __LINE__);
    MEMCACHED_ITEM_UNLINK(ITEM_key(it), it->nkey, it->nbytes);
    if ((it->it_flags & ITEM_LINKED) != 0) {
        it->it_flags &= ~ITEM_LINKED;
        STATS_LOCK();
        stats.curr_bytes -= ITEM_ntotal(it);
        stats.curr_items -= 1;
        STATS_UNLOCK();
        assoc_delete(ITEM_key(it), it->nkey, hv);
        item_unlink_q(it);
        do_item_remove(it);
    }
}

//将item从hashtable和LRU链中移除,而且还释放掉 item 所占的内存 (其实只是把 item 放到空闲链表中),是do_item_link的逆操作
void do_item_unlink(item *it, const uint32_t hv)
{
    MEMCACHED_ITEM_UNLINK(ITEM_key(it), it->nkey, it->nbytes);
    mutex_lock(&cache_lock);//执行同步
    if ((it->it_flags & ITEM_LINKED) != 0) {//判断状态值，保证item还在LRU队列中
        it->it_flags &= ~ITEM_LINKED;//修改状态值
        STATS_LOCK();//更新统计信息
        stats.curr_bytes -= ITEM_ntotal(it);
        stats.curr_items -= 1;
        STATS_UNLOCK();
        assoc_delete(ITEM_key(it), it->nkey, hv);//从Hash表中删除
        item_unlink_q(it);//将item从slabclass对应的LRU队列摘除
        do_item_remove(it);//释放 item 所占的内存
    }
    mutex_unlock(&cache_lock);
}

void do_item_unlink(item *it, const uint32_t hv) {
		syslog(LOG_INFO, "[%s:%s:%d]", __FILE__, __func__, __LINE__);
    MEMCACHED_ITEM_UNLINK(ITEM_key(it), it->nkey, it->nbytes);
    mutex_lock(&cache_lock);
    if ((it->it_flags & ITEM_LINKED) != 0) {
        it->it_flags &= ~ITEM_LINKED;//设置为非linked
        STATS_LOCK();
        stats.curr_bytes -= ITEM_ntotal(it);
        stats.curr_items -= 1;
        STATS_UNLOCK();
        assoc_delete(ITEM_key(it), it->nkey, hv); //从hash表中删除
        item_unlink_q(it); //从LRU链中删除
        do_item_remove(it);
    }
    mutex_unlock(&cache_lock);
}

int stats_prefix_delete(const char *prefix, const size_t nprefix) {
    PREFIX_STATS *curr, *next, *prev;
    int hidx;
    int ret = -1;

    STATS_LOCK();
    if (nprefix == 0) {
        hidx = mc_hash(prefix, nprefix, 0) % PREFIX_HASH_SIZE;
        prev = NULL;
        for (curr = prefix_stats[hidx]; curr != NULL; prev = curr, curr = curr->next) {
            if (curr->prefix_len == 0) break;
        }
        if (curr != NULL) { /* found */
            if (prev == NULL) prefix_stats[hidx] = curr->next;
            else              prev->next = curr->next;
            num_prefixes--;
            total_prefix_size -= strlen(null_prefix_str);

            free(curr->prefix);
            free(curr);
            ret = 0;
        }
    } else { /* nprefix > 0 */
        // Full scan for sub-prefixies (we would fix it in future)
        for (hidx = 0; hidx < PREFIX_HASH_SIZE; hidx++) {
            prev = NULL;
            for (curr = prefix_stats[hidx]; curr != NULL; curr = next) {
                next = curr->next;
                if ((curr->prefix_len >= nprefix && strncmp(curr->prefix, prefix, nprefix) == 0) &&
                    (curr->prefix_len == nprefix || *(curr->prefix+nprefix)==settings.prefix_delimiter)) {
                    if (prev == NULL) prefix_stats[hidx] = curr->next;
                    else              prev->next = curr->next;
                    num_prefixes--;
                    total_prefix_size -= curr->prefix_len;

                    free(curr->prefix);
                    free(curr);
                    ret = 0;
                } else {
                    prev = curr;
                }
            }
        }
    }
    STATS_UNLOCK();
    return ret;
}

//输出所有信息
char *stats_prefix_dump(int *length) {
    const char *format = "PREFIX %s get %llu hit %llu set %llu del %llu\r\n";
    PREFIX_STATS *pfs;
    char *buf;
    int i, pos;
    size_t size = 0, written = 0, total_written = 0;

    /*
     * Figure out how big the buffer needs to be. This is the sum of the
     * lengths of the prefixes themselves, plus the size of one copy of
     * the per-prefix output with 20-digit values for all the counts,
     * plus space for the "END" at the end.
     */
    STATS_LOCK();
    //计算需要全部内存空间大小
    size = strlen(format) + total_prefix_size +
           num_prefixes * (strlen(format) - 2 /* %s */
                           + 4 * (20 - 4)) /* %llu replaced by 20-digit num */
                           + sizeof("END\r\n");
    buf = malloc(size);
    if (NULL == buf) {
        perror("Can't allocate stats response: malloc");
        STATS_UNLOCK();
        return NULL;
    }

    pos = 0;
    for (i = 0; i < PREFIX_HASH_SIZE; i++) {
        for (pfs = prefix_stats[i]; NULL != pfs; pfs = pfs->next) {
            //格式化后拷贝到指定指针处
            written = snprintf(buf + pos, size-pos, format,
                           pfs->prefix, pfs->num_gets, pfs->num_hits,
                           pfs->num_sets, pfs->num_deletes);
            pos += written;
            total_written += written;
            //判断是否拷贝正确
            assert(total_written < size);
        }
    }

    STATS_UNLOCK();
    memcpy(buf + pos, "END\r\n", 6);

    *length = pos + 5;
    return buf;
}

//初始化哈希表
void assoc_init(const int hashtable_init) {
    //如何设置了哈希表大小，用设置大小，否则使用默认参数。
    if (hashtable_init) {
        hashpower = hashtable_init;
    }
	//申请哈希表空间
    primary_hashtable = calloc(hashsize(hashpower), sizeof(void *));
    if (! primary_hashtable) {
        fprintf(stderr, "Failed to init hashtable.\n");
        exit(EXIT_FAILURE);
    }
	//记录哈希表大小和占用字节
    STATS_LOCK();
    stats.hash_power_level = hashpower;
    stats.hash_bytes = hashsize(hashpower) * sizeof(void *);
    STATS_UNLOCK();
}