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BeladySize.c
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BeladySize.c
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//
// BeladySize.c
// libCacheSim
//
// sample object and compare reuse_distance * size, then evict the greatest one
//
//
/* todo: change to BeladySize */
#include "../../dataStructure/hashtable/hashtable.h"
#include "../../include/libCacheSim/evictionAlgo.h"
#ifdef __cplusplus
extern "C" {
#endif
// #define EXACT_Belady 1
static const char* DEFAULT_PARAMS = "n-sample=128";
typedef struct {
// how many samples to take at each eviction
int n_sample;
} BeladySize_params_t; /* BeladySize parameters */
// ***********************************************************************
// **** ****
// **** function declarations ****
// **** ****
// ***********************************************************************
static void BeladySize_parse_params(cache_t *cache,
const char *cache_specific_params);
static void BeladySize_free(cache_t *cache);
static bool BeladySize_get(cache_t *cache, const request_t *req);
static cache_obj_t *BeladySize_find(cache_t *cache, const request_t *req,
const bool update_cache);
static cache_obj_t *BeladySize_insert(cache_t *cache, const request_t *req);
static cache_obj_t *BeladySize_to_evict(cache_t *cache, const request_t *req);
static void BeladySize_evict(cache_t *cache, const request_t *req);
static bool BeladySize_remove(cache_t *cache, const obj_id_t obj_id);
static void BeladySize_remove_obj(cache_t *cache, cache_obj_t *obj);
// ***********************************************************************
// **** ****
// **** end user facing functions ****
// **** ****
// **** init, free, get ****
// ***********************************************************************
/**
* @brief initialize a Belady cache
*
* @param ccache_params some common cache parameters
* @param cache_specific_params Belady specific parameters, should be NULL
*/
cache_t *BeladySize_init(const common_cache_params_t ccache_params,
const char *cache_specific_params) {
cache_t *cache = cache_struct_init("BeladySize", ccache_params, cache_specific_params);
cache->cache_init = BeladySize_init;
cache->cache_free = BeladySize_free;
cache->get = BeladySize_get;
cache->find = BeladySize_find;
cache->insert = BeladySize_insert;
cache->evict = BeladySize_evict;
cache->remove = BeladySize_remove;
cache->to_evict = BeladySize_to_evict;
BeladySize_params_t *params =
(BeladySize_params_t *)malloc(sizeof(BeladySize_params_t));
cache->eviction_params = params;
BeladySize_parse_params(cache, DEFAULT_PARAMS);
if (cache_specific_params != NULL) {
BeladySize_parse_params(cache, cache_specific_params);
}
return cache;
}
/**
* free resources used by this cache
*
* @param cache
*/
static void BeladySize_free(cache_t *cache) {
free(cache->eviction_params);
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 BeladySize_get(cache_t *cache, const request_t *req) {
return cache_get_base(cache, req);
}
// ***********************************************************************
// **** ****
// **** developer facing APIs (used by cache developer) ****
// **** ****
// ***********************************************************************
/**
* @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
*/
static cache_obj_t *BeladySize_find(cache_t *cache, const request_t *req,
const bool update_cache) {
cache_obj_t *obj = cache_find_base(cache, req, update_cache);
if (!update_cache) {
return obj;
}
if (update_cache && obj != NULL) {
if (req->next_access_vtime == -1 || req->next_access_vtime == INT64_MAX) {
BeladySize_remove(cache, obj->obj_id);
} else {
obj->Belady.next_access_vtime = req->next_access_vtime;
}
}
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 *BeladySize_insert(cache_t *cache, const request_t *req) {
if (req->next_access_vtime == -1 || req->next_access_vtime == INT64_MAX) {
return NULL;
}
cache_obj_t *obj = cache_insert_base(cache, req);
obj->Belady.next_access_vtime = req->next_access_vtime;
return obj;
}
#ifdef EXACT_Belady
struct hash_iter_user_data {
uint64_t curr_vtime;
cache_obj_t *to_evict_obj;
uint64_t max_score;
};
static inline void hashtable_iter_Belady_size(cache_obj_t *cache_obj,
void *userdata) {
struct hash_iter_user_data *iter_userdata =
(struct hash_iter_user_data *)userdata;
if (iter_userdata->max_score == UINT64_MAX) return;
uint64_t obj_score;
if (cache_obj->Belady.next_access_vtime == -1)
obj_score = UINT64_MAX;
else
obj_score = cache_obj->obj_size * (cache_obj->Belady.next_access_vtime -
iter_userdata->curr_vtime);
if (obj_score > iter_userdata->max_score) {
iter_userdata->to_evict_obj = cache_obj;
iter_userdata->max_score = obj_score;
}
}
/**
* @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 *BeladySize_to_evict(cache_t *cache, const request_t *req) {
struct hash_iter_user_data iter_userdata;
iter_userdata.curr_vtime = cache->n_req;
iter_userdata.max_score = 0;
iter_userdata.to_evict_obj = NULL;
hashtable_foreach(cache->hashtable, hashtable_iter_Belady_size,
&iter_userdata);
return iter_userdata.to_evict_obj;
}
#else
static cache_obj_t *BeladySize_to_evict(cache_t *cache, const request_t *req) {
BeladySize_params_t *params = (BeladySize_params_t *)cache->eviction_params;
cache_obj_t *obj_to_evict = NULL, *sampled_obj;
int64_t obj_to_evict_score = -1, sampled_obj_score;
for (int i = 0; i < params->n_sample; i++) {
sampled_obj = hashtable_rand_obj(cache->hashtable);
sampled_obj_score =
(int64_t)sampled_obj->obj_size *
(int64_t)(sampled_obj->Belady.next_access_vtime - cache->n_req);
if (obj_to_evict_score < sampled_obj_score) {
obj_to_evict = sampled_obj;
obj_to_evict_score = sampled_obj_score;
}
}
if (obj_to_evict == NULL) {
WARN(
"BeladySize_to_evict: obj_to_evict is NULL, "
"maybe cache size is too small or hash power too large\n");
return BeladySize_to_evict(cache, req);
}
return obj_to_evict;
}
#endif
/**
* @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
* @param evicted_obj if not NULL, return the evicted object to caller
*/
static void BeladySize_evict(cache_t *cache, const request_t *req) {
cache_obj_t *obj_to_evict = BeladySize_to_evict(cache, req);
cache_evict_base(cache, obj_to_evict, true);
}
bool BeladySize_remove(cache_t *cache, const 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;
}
// ***********************************************************************
// **** ****
// **** parameter set up functions ****
// **** ****
// ***********************************************************************
/**
* @brief print the default parameters
*
*/
static const char *BeladySize_current_params(BeladySize_params_t *params) {
static __thread char params_str[128];
snprintf(params_str, 128, "n-sample=%d\n", params->n_sample);
return params_str;
}
/**
* parse the given parameters
* input parameter is a string,
* to see the default parameters, use current_params()
* or use -e "print" with cachesim
*/
static void BeladySize_parse_params(cache_t *cache,
const char *cache_specific_params) {
BeladySize_params_t *params = (BeladySize_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) {
params->n_sample = (int)strtol(value, &end, 0);
if (strlen(end) > 2) {
ERROR("param parsing error, find string \"%s\" after number\n", end);
}
} else if (strcasecmp(key, "print") == 0) {
printf("current parameters: %s\n", BeladySize_current_params(params));
exit(0);
} else {
ERROR("%s does not have parameter %s, support %s\n", cache->cache_name,
key, BeladySize_current_params(params));
exit(1);
}
}
free(old_params_str);
}
#ifdef __cplusplus
}
#endif