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//
// RandomLRU.c
// libCacheSim
//
// Picks two objects at random and evicts the one that is the least recently
// used RandomLRU eviction
//
// Created by Juncheng on 8/2/16.
// Copyright © 2016 Juncheng. All rights reserved.
//
#include <stdlib.h>
#include "dataStructure/hashtable/hashtable.h"
#include "libCacheSim/evictionAlgo.h"
#include "libCacheSim/macro.h"
#ifdef __cplusplus
extern "C" {
#endif
typedef struct RandomLRU_params {
int32_t n_samples;
cache_obj_t **eviction_candidates;
} RandomLRU_params_t;
static const char *DEFAULT_CACHE_PARAMS = "n-samples=16";
// ***********************************************************************
// **** ****
// **** function declarations ****
// **** ****
// ***********************************************************************
static void RandomLRU_free(cache_t *cache);
static bool RandomLRU_get(cache_t *cache, const request_t *req);
static cache_obj_t *RandomLRU_find(cache_t *cache, const request_t *req,
bool update_cache);
static cache_obj_t *RandomLRU_insert(cache_t *cache, const request_t *req);
static cache_obj_t *RandomLRU_to_evict(cache_t *cache, const request_t *req);
static void RandomLRU_evict(cache_t *cache, const request_t *req);
static bool RandomLRU_remove(cache_t *cache, obj_id_t obj_id);
static void RandomLRU_parse_params(cache_t *cache,
const char *cache_specific_params);
// ***********************************************************************
// **** ****
// **** end user facing functions ****
// **** ****
// **** init, free, get ****
// ***********************************************************************
/**
* @brief initialize a RandomLRU cache
*
* @param ccache_params some common cache parameters
* @param cache_specific_params RandomLRU specific parameters, should be NULL
*/
cache_t *RandomLRU_init(const common_cache_params_t ccache_params,
const char *cache_specific_params) {
common_cache_params_t ccache_params_copy = ccache_params;
ccache_params_copy.hashpower = MAX(12, ccache_params_copy.hashpower - 8);
cache_t *cache =
cache_struct_init("RandomLRU", ccache_params_copy, cache_specific_params);
cache->cache_init = RandomLRU_init;
cache->cache_free = RandomLRU_free;
cache->get = RandomLRU_get;
cache->find = RandomLRU_find;
cache->insert = RandomLRU_insert;
cache->to_evict = RandomLRU_to_evict;
cache->evict = RandomLRU_evict;
cache->remove = RandomLRU_remove;
cache->eviction_params =
(RandomLRU_params_t *)malloc(sizeof(RandomLRU_params_t));
RandomLRU_params_t *params = (RandomLRU_params_t *)(cache->eviction_params);
memset(params, 0, sizeof(RandomLRU_params_t));
RandomLRU_parse_params(cache, DEFAULT_CACHE_PARAMS);
if (cache_specific_params != NULL) {
RandomLRU_parse_params(cache, cache_specific_params);
}
params->eviction_candidates =
(cache_obj_t **)malloc(sizeof(cache_obj_t *) * params->n_samples);
snprintf(cache->cache_name, CACHE_NAME_ARRAY_LEN, "RandomLRU-%d",
params->n_samples);
return cache;
}
/**
* free resources used by this cache
*
* @param cache
*/
static void RandomLRU_free(cache_t *cache) {
RandomLRU_params_t *params = (RandomLRU_params_t *)(cache->eviction_params);
free(params->eviction_candidates);
cache_struct_free(cache);
}
/**
* @brief this function is the user facing API
* it performs the following logic
*
* ```
* if obj in cache:
* update_metadata
* return true
* else:
* if cache does not have enough space:
* evict until it has space to insert
* insert the object
* return false
* ```
*
* @param cache
* @param req
* @return true if cache hit, false if cache miss
*/
static bool RandomLRU_get(cache_t *cache, const request_t *req) {
return cache_get_base(cache, req);
}
// ***********************************************************************
// **** ****
// **** developer facing APIs (used by cache developer) ****
// **** ****
// ***********************************************************************
/**
* @brief check whether an object is 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 true on hit, false on miss
*/
static cache_obj_t *RandomLRU_find(cache_t *cache, const request_t *req,
bool update_cache) {
cache_obj_t *obj = cache_find_base(cache, req, update_cache);
if (obj != NULL && update_cache) {
obj->Random.last_access_vtime = cache->n_req;
}
return obj;
}
/**
* @brief insert an object into the cache,
* update the hash table and cache metadata
* this function assumes the cache has enough space
* and eviction is not part of this function
*
* @param cache
* @param req
* @return the inserted object
*/
static cache_obj_t *RandomLRU_insert(cache_t *cache, const request_t *req) {
cache_obj_t *obj = cache_insert_base(cache, req);
obj->Random.last_access_vtime = cache->n_req;
return obj;
}
/**
* @brief find the object to be evicted
* this function does not actually evict the object or update metadata
* not all eviction algorithms support this function
* because the eviction logic cannot be decoupled from finding eviction
* candidate, so use assert(false) if you cannot support this function
*
* @param cache the cache
* @return the object to be evicted
*/
static cache_obj_t *RandomLRU_to_evict(cache_t *cache, const request_t *req) {
// cache_obj_t *obj_to_evict1 = hashtable_rand_obj(cache->hashtable);
// cache_obj_t *obj_to_evict2 = hashtable_rand_obj(cache->hashtable);
// const int N = 16;
// cache_objt_t *obj_to_evict[N];
// for (int i = 0; i < N; i++) {
// obj_to_evict[i] = hashtable_rand_obj(cache->hashtable);
// }
// qsort(obj_to_evict, N, sizeof(cache_obj_t *), compare);
// if (obj_to_evict1->Random.last_access_vtime <
// obj_to_evict2->Random.last_access_vtime)
// return obj_to_evict1;
// else
// return obj_to_evict2;
assert(false);
return NULL;
}
static int compare_access_time(const void *p1, const void *p2) {
const cache_obj_t *obj1 = *(const cache_obj_t **)p1;
const cache_obj_t *obj2 = *(const cache_obj_t **)p2;
if (obj1->Random.last_access_vtime < obj2->Random.last_access_vtime) {
return -1;
} else if (obj1->Random.last_access_vtime > obj2->Random.last_access_vtime) {
return 1;
} else {
return 0;
}
}
/**
* @brief evict an object from the cache
* it needs to call cache_evict_base before returning
* which updates some metadata such as n_obj, occupied size, and hash table
*
* @param cache
* @param req not used
*/
static void RandomLRU_evict(cache_t *cache, const request_t *req) {
RandomLRU_params_t *params = (RandomLRU_params_t *)(cache->eviction_params);
for (int i = 0; i < params->n_samples; i++) {
params->eviction_candidates[i] = hashtable_rand_obj(cache->hashtable);
}
qsort(params->eviction_candidates, params->n_samples, sizeof(cache_obj_t *),
compare_access_time);
cache_evict_base(cache, params->eviction_candidates[0], true);
}
/**
* @brief remove an object from the cache
* this is different from cache_evict because it is used to for user trigger
* remove, and eviction is used by the cache to make space for new objects
*
* it needs to call cache_remove_obj_base before returning
* which updates some metadata such as n_obj, occupied size, and hash table
*
* @param cache
* @param obj_id
* @return true if the object is removed, false if the object is not in the
* cache
*/
static bool RandomLRU_remove(cache_t *cache, obj_id_t obj_id) {
cache_obj_t *obj = hashtable_find_obj_id(cache->hashtable, obj_id);
if (obj == NULL) {
return false;
}
cache_remove_obj_base(cache, obj, true);
return true;
}
static void RandomLRU_parse_params(cache_t *cache,
const char *cache_specific_params) {
RandomLRU_params_t *params = (RandomLRU_params_t *)(cache->eviction_params);
char *params_str = strdup(cache_specific_params);
char *old_params_str = params_str;
char *end;
while (params_str != NULL && params_str[0] != '\0') {
/* different parameters are separated by comma,
* key and value are separated by = */
char *key = strsep((char **)¶ms_str, "=");
char *value = strsep((char **)¶ms_str, ",");
// skip the white space
while (params_str != NULL && *params_str == ' ') {
params_str++;
}
if (strcasecmp(key, "n-sample") == 0 || strcasecmp(key, "n-samples") == 0) {
params->n_samples = (int)strtol(value, &end, 0);
} else if (strcasecmp(key, "print") == 0) {
printf("current parameters: n-samples=%d\n", params->n_samples);
exit(0);
} else {
ERROR("%s does not have parameter %s\n", cache->cache_name, key);
exit(1);
}
}
free(old_params_str);
}
#ifdef __cplusplus
}
#endif
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