Function ARC_find

libCacheSim/cache/eviction/ARC.c:219–294

* @brief find an object in the cache * * @param cache * @param req * @param update_cache whether to update the cache, * if true, the object is promoted * and if the object is expired, it is removed from the cache * @return the object or NULL if not found */

 * @return the object or NULL if not found
 */
static cache_obj_t *ARC_find(cache_t *cache, const request_t *req,
                             const bool update_cache) {
  ARC_params_t *params = (ARC_params_t *)(cache->eviction_params);

  cache_obj_t *obj = cache_find_base(cache, req, update_cache);

  if (!update_cache) {
    return obj->ARC.ghost ? NULL : obj;
  }

  if (obj == NULL) {
    return NULL;
  }

  params->curr_obj_in_L1_ghost = false;
  params->curr_obj_in_L2_ghost = false;

  int lru_id = obj->ARC.lru_id;
  cache_obj_t *ret = obj;

  if (obj->ARC.ghost) {
    // ghost hit
    ret = NULL;
    params->vtime_last_req_in_ghost = cache->n_req;
    // cache miss, but hit on thost
    if (obj->ARC.lru_id == 1) {
      params->curr_obj_in_L1_ghost = true;
      // case II: x in L1_ghost
      DEBUG_ASSERT(params->L1_ghost_size >= 1);
      double delta =
          MAX((double)params->L2_ghost_size / params->L1_ghost_size, 1);
      params->p = MIN(params->p + delta, cache->cache_size);
      params->L1_ghost_size -= obj->obj_size + cache->obj_md_size;
      remove_obj_from_list(&params->L1_ghost_head, &params->L1_ghost_tail, obj);
    } else {
      params->curr_obj_in_L2_ghost = true;
      // case III: x in L2_ghost
      DEBUG_ASSERT(params->L2_ghost_size >= 1);
      double delta =
          MAX((double)params->L1_ghost_size / params->L2_ghost_size, 1);
      params->p = MAX(params->p - delta, 0);
      params->L2_ghost_size -= obj->obj_size + cache->obj_md_size;
      remove_obj_from_list(&params->L2_ghost_head, &params->L2_ghost_tail, obj);
    }

    hashtable_delete(cache->hashtable, obj);
  } else {
    // cache hit, case I: x in L1_data or L2_data
#ifdef USE_BELADY
    if (obj->next_access_vtime == INT64_MAX) {
      return ret;
    }
#endif

    if (lru_id == 1) {
      // move to LRU2
      obj->ARC.lru_id = 2;
      remove_obj_from_list(&params->L1_data_head, &params->L1_data_tail, obj);