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Hyperbolic.c
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Hyperbolic.c
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/* Hyperbolic caching */
#include "../../dataStructure/hashtable/hashtable.h"
#include "../../include/libCacheSim/evictionAlgo.h"
#ifdef __cplusplus
extern "C" {
#endif
typedef struct Hyperbolic_params {
int n_sample;
} Hyperbolic_params_t;
// ***********************************************************************
// **** ****
// **** function declarations ****
// **** ****
// ***********************************************************************
static void Hyperbolic_parse_params(cache_t *cache,
const char *cache_specific_params);
static void Hyperbolic_free(cache_t *cache);
static bool Hyperbolic_get(cache_t *cache, const request_t *req);
static cache_obj_t *Hyperbolic_find(cache_t *cache, const request_t *req,
const bool update_cache);
static cache_obj_t *Hyperbolic_insert(cache_t *cache, const request_t *req);
static cache_obj_t *Hyperbolic_to_evict(cache_t *cache, const request_t *req);
static void Hyperbolic_evict(cache_t *cache, const request_t *req);
static bool Hyperbolic_remove(cache_t *cache, const obj_id_t obj_id);
// ***********************************************************************
// **** ****
// **** end user facing functions ****
// **** ****
// ***********************************************************************
/**
* @brief initialize a cache
*
* @param ccache_params some common cache parameters
* @param cache_specific_params cache specific parameters, see parse_params
* function or use -e "print" with the cachesim binary
*/
cache_t *Hyperbolic_init(const common_cache_params_t ccache_params,
const char *cache_specific_params) {
// reduce hash table size to make sampling faster
common_cache_params_t ccache_params_local = ccache_params;
ccache_params_local.hashpower = MAX(12, ccache_params_local.hashpower - 8);
cache_t *cache = cache_struct_init("Hyperbolic", ccache_params_local, cache_specific_params);
cache->cache_init = Hyperbolic_init;
cache->cache_free = Hyperbolic_free;
cache->get = Hyperbolic_get;
cache->find = Hyperbolic_find;
cache->insert = Hyperbolic_insert;
cache->evict = Hyperbolic_evict;
cache->remove = Hyperbolic_remove;
cache->to_evict = Hyperbolic_to_evict;
Hyperbolic_params_t *params = my_malloc(Hyperbolic_params_t);
params->n_sample = 64;
cache->eviction_params = params;
if (cache_specific_params != NULL) {
Hyperbolic_parse_params(cache, cache_specific_params);
}
if (ccache_params.consider_obj_metadata) {
// freq + age
cache->obj_md_size = 8 + 8;
} else {
cache->obj_md_size = 0;
}
return cache;
}
/**
* free resources used by this cache
*
* @param cache
*/
static void Hyperbolic_free(cache_t *cache) {
Hyperbolic_params_t *params = cache->eviction_params;
my_free(sizeof(Hyperbolic_params_t), 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 Hyperbolic_get(cache_t *cache, const request_t *req) {
bool ret = cache_get_base(cache, req);
return ret;
}
// ***********************************************************************
// **** ****
// **** 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 *Hyperbolic_find(cache_t *cache, const request_t *req,
const bool update_cache) {
cache_obj_t *cache_obj = cache_find_base(cache, req, update_cache);
if (update_cache && cache_obj) {
cache_obj->hyperbolic.freq++;
}
return cache_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 *Hyperbolic_insert(cache_t *cache, const request_t *req) {
cache_obj_t *cached_obj = cache_insert_base(cache, req);
cached_obj->hyperbolic.freq = 1;
cached_obj->hyperbolic.vtime_enter_cache = cache->n_req;
return cached_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 *Hyperbolic_to_evict(cache_t *cache, const request_t *req) {
Hyperbolic_params_t *params = cache->eviction_params;
cache_obj_t *best_candidate = NULL, *sampled_obj;
double best_candidate_score = 1.0e16, sampled_obj_score;
for (int i = 0; i < params->n_sample; i++) {
sampled_obj = hashtable_rand_obj(cache->hashtable);
double age =
(double)(cache->n_req - sampled_obj->hyperbolic.vtime_enter_cache);
sampled_obj_score = 1.0e8 * (double)sampled_obj->hyperbolic.freq / age;
if (best_candidate_score > sampled_obj_score) {
best_candidate = sampled_obj;
best_candidate_score = sampled_obj_score;
}
}
cache->to_evict_candidate = best_candidate;
cache->to_evict_candidate_gen_vtime = cache->n_req;
return best_candidate;
}
/**
* @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 Hyperbolic_evict(cache_t *cache,
__attribute__((unused)) const request_t *req) {
cache_obj_t *obj_to_evict = NULL;
if (cache->to_evict_candidate_gen_vtime == cache->n_req) {
obj_to_evict = cache->to_evict_candidate;
} else {
obj_to_evict = Hyperbolic_to_evict(cache, req);
}
cache->to_evict_candidate_gen_vtime = -1;
if (obj_to_evict == NULL) {
DEBUG_ASSERT(cache->n_obj == 0);
WARN("no object can be evicted\n");
}
cache_evict_base(cache, obj_to_evict, true);
}
static void Hyperbolic_remove_obj(cache_t *cache, cache_obj_t *obj) {
cache_remove_obj_base(cache, obj, 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 Hyperbolic_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;
}
Hyperbolic_remove_obj(cache, obj);
return true;
}
// ***********************************************************************
// **** ****
// **** parameter set up functions ****
// **** ****
// ***********************************************************************
static const char *Hyperbolic_current_params(Hyperbolic_params_t *params) {
static __thread char params_str[128];
snprintf(params_str, 128, "n-sample=%d\n", params->n_sample);
return params_str;
}
static void Hyperbolic_parse_params(cache_t *cache,
const char *cache_specific_params) {
char *end;
Hyperbolic_params_t *params = (Hyperbolic_params_t *)cache->eviction_params;
char *params_str = strdup(cache_specific_params);
char *old_params_str = params_str;
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("parameters: %s\n", Hyperbolic_current_params(params));
exit(0);
} else {
ERROR("%s does not have parameter %s, support %s\n", cache->cache_name,
key, Hyperbolic_current_params(params));
exit(1);
}
}
free(old_params_str);
}
#ifdef __cplusplus
}
#endif