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/*
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******************************************************************************
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* INTERPEAK API HEADER FILE
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*
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* Document no: @(#) $Name: VXWORKS_ITER40_2019102207 $ $RCSfile: ipcom_cache.h,v $ $Revision: 1.3 $
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* $Source: /home/interpeak/CVSRoot/ipcom/include/ipcom_cache.h,v $
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* $Author: kenneth $ $Date: 2009-06-22 21:22:03 $
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* $State: Exp $ $Locker: $
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*
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* INTERPEAK_COPYRIGHT_STRING
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* Design and implementation by Kenneth Jonsson <kenneth.jonsson@windriver.com>
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******************************************************************************
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*/
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#ifndef IPCOM_CACHE_H
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#define IPCOM_CACHE_H
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/*
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****************************************************************************
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* 1 DESCRIPTION
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****************************************************************************
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* Implements a N-set associative cache for constant sized
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* objects. Lookup and insert operations are always O(1), flush are
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* always O(H) where H is the size of the cache index hash table(s).
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*
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* The memory gived to the cache is partition in two parts, first part
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* (which is relativly small) is the cache index hash table(s). The
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* cache index consists of N (where N is the set associativity of the
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* cache) hash tables. The information stored in the hash table in an
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* index into the 2:nd part of the cache, which is the object array.
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*
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* This partition of the cache allows for 100% usage of the
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* objects. That is a benefit of having the objects directly in the
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* hash table if obj_size is a lot larger than
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* sizeof(Ipcom_cache_index).
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*
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* The memory is partition as this:
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* (1) total_mem >= obj_cnt * obj_size
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* + htbl_cnt * sizeof(Ipcom_cache_index_set)
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* (2) C = htbl_cnt * IPCOM_CACHE_SET_N
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* (3) obj_cnt = C * IPCOM_CACHE_FILL_RATIO / 100
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*
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*/
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/*
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****************************************************************************
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* 2 CONFIGURATION
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****************************************************************************
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*/
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#include "ipcom_config.h"
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/*
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* Number of set the cache index should have. This is the number of
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* collisions in the hash table the cache can handle before entries
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* has to be removed from the cache. Increasing this number will
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* increase the efficiency of the cache index. Increasing this number
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* also means that the time it takes to find an object or determine
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* that a lookup fails increases.
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*/
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#define IPCOM_CACHE_SET_N 16
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/*
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* The ratio between the number of objects and the number of buckets
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* in the hash table. This number is in percent. A number of X means
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* that there will be X% as many objects as there is buckets. Higher
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* ration means less cache efficiency, but more of the memory used by
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* the cache are used for storing objects objects. A reasonably range
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* is 40-80.
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*/
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#define IPCOM_CACHE_FILL_RATIO 50
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/*
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* Define if the cache should keep track of statistics.
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* NOTE: keep track of statistics will make the cache slightly
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* slower.
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*/
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#define IPCOM_CACHE_USE_STATS
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/*
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****************************************************************************
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* 3 INCLUDE FILES
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****************************************************************************
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*/
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#include <ipcom_type.h>
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#include <ipcom_cstyle.h>
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#include <ipcom_hash.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/*
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****************************************************************************
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* 4 DEFINES
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****************************************************************************
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*/
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/*
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* This index value is used in a bucket that does not refer to any object.
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*/
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#define IPCOM_CACHE_INVALID_INDEX ((Ipcom_cache_index) ~0)
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#ifdef IPCOM_CACHE_USE_STATS
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#define IPCOM_CACHE_STATS(x) (x)
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#else
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#define IPCOM_CACHE_STATS(x)
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#endif
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/*
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****************************************************************************
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* 5 TYPES
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****************************************************************************
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*/
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/*
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* The definition of Ipcom_cache_index determines the maximum number
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* of objects the cache can hold. Possible definitions are Ip_u8,
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* Ip_u16 or Ip_u32 for a maximum of 2^8-1, 2^16-1 or 2^32-1 objects.
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* NOTE: A higher maximum object count means that the index hash table
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* will take more memory for the SAME amount of hash buckets since the
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* size of a hash bucket is directly proportional to
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* sizeof(Ipcom_cache_index)
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*/
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typedef Ip_u16 Ipcom_cache_index;
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#ifdef IPCOM_CACHE_USE_STATS
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/*
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* Statistics counters for the cachex
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*/
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struct Ipcom_cache_stats {
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unsigned inserts; /* Number of objects inserted in the cache */
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unsigned bucketshares; /* Number of hash buckets that has more
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than one entry queued */
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unsigned collisions; /* Number of objects that had to be
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deleted due to hash collisions */
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unsigned recycles; /* Number of times a valid object had to be
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recycled since there were no free once */
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unsigned lookups; /* Number of lookups done */
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unsigned misses; /* Number of unsuccessful lookups */
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};
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#endif
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/*
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* Each cache index entry represents all objects that hash to the same
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* index.
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*/
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typedef struct Ipcom_cache_index_set_t {
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Ipcom_cache_index obj_idx[IPCOM_CACHE_SET_N];
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}
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Ipcom_cache_index_set;
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/*
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* Representation of a free object.
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*/
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typedef struct Ipcom_cache_free_obj_t {
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struct Ipcom_cache_free_obj_t *next;
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}
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Ipcom_cache_free_obj;
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/*
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* Represent one cache instance
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*/
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typedef struct Ipcom_cache_t {
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Ipcom_hash_obj_func obj_func;
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Ipcom_hash_key_func key_func;
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Ipcom_hash_cmp_func cmp_func;
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unsigned htbl_cnt; /* Number of buckets in 'htbl' */
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Ipcom_cache_index_set *htbl; /* Hash table of indexes into the
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'objs' array */
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unsigned obj_size; /* Space used by each object */
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unsigned obj_order; /* Each object occupies (1 << obj_order) */
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Ipcom_cache_index obj_cnt; /* Number of objects in 'objs' */
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void *objs; /* Pointer to the first object */
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Ipcom_cache_free_obj *free_objs; /* List of free objects */
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#ifdef IPCOM_CACHE_USE_STATS
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struct Ipcom_cache_stats stats;
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#endif
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}
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Ipcom_cache;
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/*
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****************************************************************************
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* 6 FUNCTIONS
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****************************************************************************
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*/
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IP_PUBLIC void ipcom_cache_delete(Ipcom_cache *cache);
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IP_PUBLIC Ipcom_cache * ipcom_cache_new_with_bucket_count(unsigned obj_cnt,
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unsigned obj_size,
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Ipcom_hash_obj_func obj_func,
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Ipcom_hash_key_func key_func,
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Ipcom_hash_cmp_func cmp_func);
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IP_PUBLIC Ipcom_cache * ipcom_cache_new_with_memory_limit(unsigned memory_limit,
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unsigned obj_size,
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Ipcom_hash_obj_func obj_func,
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Ipcom_hash_key_func key_func,
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Ipcom_hash_cmp_func cmp_func);
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IP_PUBLIC void ipcom_cache_flush(Ipcom_cache *cache);
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IP_PUBLIC void ipcom_cache_insert(Ipcom_cache *cache, void *obj);
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IP_PUBLIC void ipcom_cache_insert_with_index(Ipcom_cache *cache,
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void *obj,
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unsigned hidx);
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IP_PUBLIC void * ipcom_cache_lookup(Ipcom_cache *cache, const void *key);
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/*
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*===========================================================================
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* ipcom_cache_index_to_obj
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*===========================================================================
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* Description: Returns the object with the specified index
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* Parameters: cache - cache instance
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* idx - object index
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* Returns:
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*
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*/
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IP_INLINE void *
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ipcom_cache_index_to_obj(Ipcom_cache *cache, Ipcom_cache_index idx)
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{
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return &(((char *) cache->objs)[idx << cache->obj_order]);
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}
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/*
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*===========================================================================
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* ipcom_cache_lookup_with_index
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*===========================================================================
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* Description: Lookups an object using a pre-calculated hash
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* value. This function can be when the hash value is
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* calculated by hardware.
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* Parameters: cache - cache instance
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* key - lookup key
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* hidx - the hash index the lookup key would produce
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* Returns: The matching object or IP_NULL if no match was found
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*
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*/
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IP_INLINE void *
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ipcom_cache_lookup_with_index(Ipcom_cache *cache,
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const void *key,
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unsigned hidx)
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{
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unsigned set_idx;
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void *obj;
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Ipcom_cache_index obj_idx;
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Ipcom_cache_index_set *obj_set = &cache->htbl[hidx];
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IPCOM_CACHE_STATS(++cache->stats.lookups);
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for (set_idx = 0; set_idx < IPCOM_CACHE_SET_N; ++set_idx)
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{
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obj_idx = obj_set->obj_idx[set_idx];
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if (IP_UNLIKELY(obj_idx == IPCOM_CACHE_INVALID_INDEX))
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break;
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obj = ipcom_cache_index_to_obj(cache, obj_idx);
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if (cache->cmp_func(obj, key))
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return obj;
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}
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IPCOM_CACHE_STATS(++cache->stats.misses);
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return IP_NULL;
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}
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#ifdef __cplusplus
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}
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#endif
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#endif
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/*
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****************************************************************************
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* END OF FILE
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****************************************************************************
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*/
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