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/* GDSF: greedy dual frequency size */
#include <cassert>
#include "abstractRank.hpp"
namespace eviction {
class GDSF : public abstractRank {
public:
GDSF() = default;
double pri_last_evict = 0.0;
};
} // namespace eviction
#ifdef __cplusplus
extern "C" {
#endif
// ***********************************************************************
// **** ****
// **** function declarations ****
// **** ****
// ***********************************************************************
cache_t *GDSF_init(const common_cache_params_t ccache_params,
const char *cache_specific_params);
static void GDSF_free(cache_t *cache);
static bool GDSF_get(cache_t *cache, const request_t *req);
static cache_obj_t *GDSF_find(cache_t *cache, const request_t *req,
bool update_cache);
static cache_obj_t *GDSF_insert(cache_t *cache, const request_t *req);
static cache_obj_t *GDSF_to_evict(cache_t *cache, const request_t *req);
static void GDSF_evict(cache_t *cache, const request_t *req);
static bool GDSF_remove(cache_t *cache, obj_id_t obj_id);
// ***********************************************************************
// **** ****
// **** end user facing functions ****
// **** ****
// **** init, free, get ****
// ***********************************************************************
/**
* @brief initialize the 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 *GDSF_init(const common_cache_params_t ccache_params,
const char *cache_specific_params) {
cache_t *cache =
cache_struct_init("GDSF", ccache_params, cache_specific_params);
cache->eviction_params = reinterpret_cast<void *>(new eviction::GDSF);
cache->cache_init = GDSF_init;
cache->cache_free = GDSF_free;
cache->get = GDSF_get;
cache->find = GDSF_find;
cache->insert = GDSF_insert;
cache->evict = GDSF_evict;
cache->to_evict = GDSF_to_evict;
cache->remove = GDSF_remove;
if (ccache_params.consider_obj_metadata) {
// freq + priority
cache->obj_md_size = 8;
} else {
cache->obj_md_size = 0;
}
return cache;
}
/**
* free resources used by this cache
*
* @param cache
*/
static void GDSF_free(cache_t *cache) {
delete reinterpret_cast<eviction::GDSF *>(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 GDSF_get(cache_t *cache, const request_t *req) {
auto *gdsf = reinterpret_cast<eviction::GDSF *>(cache->eviction_params);
cache_obj_t *obj = cache->find(cache, req, true);
bool hit = (obj != NULL);
if (!hit && cache->can_insert(cache, req)) {
cache->insert(cache, req);
while (cache->get_occupied_byte(cache) > cache->cache_size) {
cache->evict(cache, req);
}
}
DEBUG_ASSERT((int64_t)gdsf->pq.size() == cache->n_obj);
DEBUG_ASSERT((int64_t)gdsf->pq_map.size() == cache->n_obj);
return hit;
}
// ***********************************************************************
// **** ****
// **** 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 *GDSF_find(cache_t *cache, const request_t *req,
bool update_cache) {
cache->n_req += 1;
auto *gdsf = reinterpret_cast<eviction::GDSF *>(cache->eviction_params);
cache_obj_t *obj = cache_find_base(cache, req, update_cache);
/* this does not consider object size change */
if (obj != nullptr && update_cache) {
/* misc frequency is updated in cache_find_base */
// obj->misc.freq += 1;
auto node = gdsf->pq_map[obj];
gdsf->pq.erase(node);
double pri =
gdsf->pri_last_evict + (double)(obj->misc.freq) * 1.0e6 / obj->obj_size;
eviction::pq_node_type new_node = {obj, pri, cache->n_req};
gdsf->pq.insert(new_node);
gdsf->pq_map[obj] = new_node;
}
return obj;
}
static bool GDSF_can_insert(cache_t *cache, const request_t *req) {
static __thread int64_t n_insert = 0, n_cannot_insert = 0;
auto *gdsf = reinterpret_cast<eviction::GDSF *>(cache->eviction_params);
if (cache->get_occupied_byte(cache) + req->obj_size <= cache->cache_size) {
return true;
}
if (req->obj_size > cache->cache_size) {
return false;
}
int64_t to_evict_size =
req->obj_size - (cache->cache_size - cache->get_occupied_byte(cache));
double pri = gdsf->pri_last_evict + 1.0e6 / req->obj_size;
bool can_insert = true;
auto iter = gdsf->pq.begin();
int n_evict = 0;
while (to_evict_size > 0) {
assert(iter != gdsf->pq.end());
assert(iter->obj->obj_id != req->obj_id);
n_evict += 1;
if (iter->priority > pri) {
// the incoming object will be evicted so not insert it
can_insert = false;
break;
}
to_evict_size -= iter->obj->obj_size;
iter++;
}
if (can_insert) {
n_insert += 1;
} else {
n_cannot_insert += 1;
}
if ((n_insert + n_cannot_insert) % 100000 == 0) {
if ((double)n_cannot_insert / (n_insert + n_cannot_insert) > 0.01)
DEBUG("size %lld n_insert %lld, n_cannot_insert %lld, ratio %.2f\n",
(long long)cache->cache_size, (long long)n_insert,
(long long)n_cannot_insert,
(double)n_cannot_insert / (n_insert + n_cannot_insert));
}
return can_insert;
}
/**
* @brief insert an object into the cache,
* update the hash table and cache metadata
* this function assumes the cache has enough space
* eviction should be
* performed before calling this function
*
* @param cache
* @param req
* @return the inserted object
*/
static cache_obj_t *GDSF_insert(cache_t *cache, const request_t *req) {
auto *gdsf = reinterpret_cast<eviction::GDSF *>(cache->eviction_params);
// this does not affect insertion for most workloads unless object size is too
// large however, when it have effect, it often increases miss ratio because a
// list of small objects (with relatively large priority) will stop the
// insertion of a large object, however, the newly requested large object is
// likely to be more useful than the small objects if (!GDSF_can_insert(cache,
// req)) return nullptr;
cache_obj_t *obj = cache_insert_base(cache, req);
DEBUG_ASSERT(obj != nullptr);
obj->misc.freq = 1;
double pri = gdsf->pri_last_evict + 1.0e6 / obj->obj_size;
eviction::pq_node_type new_node = {obj, pri, cache->n_req};
auto r = gdsf->pq.insert(new_node);
DEBUG_ASSERT(r.second);
gdsf->pq_map[obj] = new_node;
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 *GDSF_to_evict(cache_t *cache, const request_t *req) {
auto *gdsf = reinterpret_cast<eviction::GDSF *>(cache->eviction_params);
eviction::pq_node_type p = gdsf->peek_lowest_score();
return p.obj;
}
/**
* @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 GDSF_evict(cache_t *cache, const request_t *req) {
auto *gdsf = reinterpret_cast<eviction::GDSF *>(cache->eviction_params);
eviction::pq_node_type p = gdsf->pop_lowest_score();
cache_obj_t *obj = p.obj;
gdsf->pri_last_evict = p.priority;
cache_remove_obj_base(cache, obj, true);
}
static void GDSF_remove_obj(cache_t *cache, cache_obj_t *obj) {
auto *gdsf = reinterpret_cast<eviction::GDSF *>(cache->eviction_params);
gdsf->remove_obj(cache, obj);
}
/**
* @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 GDSF_remove(cache_t *cache, obj_id_t obj_id) {
auto *gdsf = reinterpret_cast<eviction::GDSF *>(cache->eviction_params);
return gdsf->remove(cache, obj_id);
}
#ifdef __cplusplus
}
#endif
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