/**
* @file
- * Simple cache implementation.
+ * Improved cache implementation.
*
- * We simply have fixed size array, and destroy previous values on collision.
+ * Fixed size array with linear probing on collision and LRU eviction
+ * on full.
*
* @author Jose Fonseca <jfonseca@vmware.com>
*/
#include "pipe/p_compiler.h"
-#include "pipe/p_debug.h"
+#include "util/u_debug.h"
#include "util/u_math.h"
#include "util/u_memory.h"
#include "util/u_cache.h"
+#include "util/simple_list.h"
struct util_cache_entry
{
+ enum { EMPTY = 0, FILLED, DELETED } state;
+ uint32_t hash;
+
+ struct util_cache_entry *next;
+ struct util_cache_entry *prev;
+
void *key;
void *value;
/** Destroy a (key, value) pair */
void (*destroy)(void *key, void *value);
+ /** Max entries in the cache */
uint32_t size;
+ /** Array [size] of entries */
struct util_cache_entry *entries;
-#ifdef DEBUG
+ /** Number of entries in the cache */
unsigned count;
-#endif
+
+ /** Head of list, sorted from Least-recently used to Most-recently used */
+ struct util_cache_entry lru;
};
+static void
+ensure_sanity(const struct util_cache *cache);
+
+#define CACHE_DEFAULT_ALPHA 2
+
+/**
+ * Create a new cache with 'size' entries. Also provide functions for
+ * hashing keys, comparing keys and destroying (key,value) pairs.
+ */
struct util_cache *
util_cache_create(uint32_t (*hash)(const void *key),
int (*compare)(const void *key1, const void *key2),
struct util_cache *cache;
cache = CALLOC_STRUCT(util_cache);
- if(!cache)
+ if (!cache)
return NULL;
cache->hash = hash;
cache->compare = compare;
cache->destroy = destroy;
+
+ make_empty_list(&cache->lru);
+
+ size *= CACHE_DEFAULT_ALPHA;
cache->size = size;
cache->entries = CALLOC(size, sizeof(struct util_cache_entry));
- if(!cache->entries) {
+ if (!cache->entries) {
FREE(cache);
return NULL;
}
+ ensure_sanity(cache);
return cache;
}
-static INLINE struct util_cache_entry *
+/**
+ * Try to find a cache entry, given the key and hash of the key.
+ */
+static struct util_cache_entry *
util_cache_entry_get(struct util_cache *cache,
+ uint32_t hash,
const void *key)
{
- uint32_t hash;
-
- hash = cache->hash(key);
+ struct util_cache_entry *first_unfilled = NULL;
+ uint32_t index = hash % cache->size;
+ uint32_t probe;
+
+ /* Probe until we find either a matching FILLED entry or an EMPTY
+ * slot (which has never been occupied).
+ *
+ * Deleted or non-matching slots are not indicative of completion
+ * as a previous linear probe for the same key could have continued
+ * past this point.
+ */
+ for (probe = 0; probe < cache->size; probe++) {
+ uint32_t i = (index + probe) % cache->size;
+ struct util_cache_entry *current = &cache->entries[i];
- return &cache->entries[hash % cache->size];
+ if (current->state == FILLED) {
+ if (current->hash == hash &&
+ cache->compare(key, current->key) == 0)
+ return current;
+ }
+ else {
+ if (!first_unfilled)
+ first_unfilled = current;
+
+ if (current->state == EMPTY)
+ return first_unfilled;
+ }
+ }
+
+ return NULL;
}
-static INLINE void
+static inline void
util_cache_entry_destroy(struct util_cache *cache,
struct util_cache_entry *entry)
{
entry->key = NULL;
entry->value = NULL;
- if(key || value)
- if(cache->destroy)
+ if (entry->state == FILLED) {
+ remove_from_list(entry);
+ cache->count--;
+
+ if (cache->destroy)
cache->destroy(key, value);
+
+ entry->state = DELETED;
+ }
}
+/**
+ * Insert an entry in the cache, given the key and value.
+ */
void
util_cache_set(struct util_cache *cache,
void *key,
void *value)
{
struct util_cache_entry *entry;
+ uint32_t hash;
assert(cache);
+ if (!cache)
+ return;
+ hash = cache->hash(key);
+ entry = util_cache_entry_get(cache, hash, key);
+ if (!entry)
+ entry = cache->lru.prev;
+
+ if (cache->count >= cache->size / CACHE_DEFAULT_ALPHA)
+ util_cache_entry_destroy(cache, cache->lru.prev);
- entry = util_cache_entry_get(cache, key);
util_cache_entry_destroy(cache, entry);
#ifdef DEBUG
++entry->count;
- ++cache->count;
#endif
entry->key = key;
+ entry->hash = hash;
entry->value = value;
+ entry->state = FILLED;
+ insert_at_head(&cache->lru, entry);
+ cache->count++;
+
+ ensure_sanity(cache);
}
+/**
+ * Search the cache for an entry with the given key. Return the corresponding
+ * value or NULL if not found.
+ */
void *
util_cache_get(struct util_cache *cache,
const void *key)
{
struct util_cache_entry *entry;
+ uint32_t hash;
assert(cache);
-
- entry = util_cache_entry_get(cache, key);
- if(!entry->key && !entry->value)
+ if (!cache)
return NULL;
-
- if(cache->compare(key, entry->key) != 0)
+ hash = cache->hash(key);
+ entry = util_cache_entry_get(cache, hash, key);
+ if (!entry)
return NULL;
+
+ if (entry->state == FILLED)
+ move_to_head(&cache->lru, entry);
return entry->value;
}
+/**
+ * Remove all entries from the cache. The 'destroy' function will be called
+ * for each entry's (key, value).
+ */
void
util_cache_clear(struct util_cache *cache)
{
uint32_t i;
assert(cache);
-
- for(i = 0; i < cache->size; ++i)
+ if (!cache)
+ return;
+
+ for (i = 0; i < cache->size; ++i) {
util_cache_entry_destroy(cache, &cache->entries[i]);
+ cache->entries[i].state = EMPTY;
+ }
+
+ assert(cache->count == 0);
+ assert(is_empty_list(&cache->lru));
+ ensure_sanity(cache);
}
+/**
+ * Destroy the cache and all entries.
+ */
void
util_cache_destroy(struct util_cache *cache)
{
assert(cache);
+ if (!cache)
+ return;
#ifdef DEBUG
- if(cache->count >= 20*cache->size) {
+ if (cache->count >= 20*cache->size) {
/* Normal approximation of the Poisson distribution */
double mean = (double)cache->count/(double)cache->size;
double stddev = sqrt(mean);
unsigned i;
- for(i = 0; i < cache->size; ++i) {
- double z = fabs(cache->count - mean)/stddev;
+ for (i = 0; i < cache->size; ++i) {
+ double z = fabs(cache->entries[i].count - mean)/stddev;
/* This assert should not fail 99.9999998027% of the times, unless
* the hash function is a poor one */
assert(z <= 6.0);
FREE(cache->entries);
FREE(cache);
}
+
+
+/**
+ * Remove the cache entry which matches the given key.
+ */
+void
+util_cache_remove(struct util_cache *cache,
+ const void *key)
+{
+ struct util_cache_entry *entry;
+ uint32_t hash;
+
+ assert(cache);
+ if (!cache)
+ return;
+
+ hash = cache->hash(key);
+
+ entry = util_cache_entry_get(cache, hash, key);
+ if (!entry)
+ return;
+
+ if (entry->state == FILLED)
+ util_cache_entry_destroy(cache, entry);
+
+ ensure_sanity(cache);
+}
+
+
+static void
+ensure_sanity(const struct util_cache *cache)
+{
+#ifdef DEBUG
+ unsigned i, cnt = 0;
+
+ assert(cache);
+ for (i = 0; i < cache->size; i++) {
+ struct util_cache_entry *header = &cache->entries[i];
+
+ assert(header);
+ assert(header->state == FILLED ||
+ header->state == EMPTY ||
+ header->state == DELETED);
+ if (header->state == FILLED) {
+ cnt++;
+ assert(header->hash == cache->hash(header->key));
+ }
+ }
+
+ assert(cnt == cache->count);
+ assert(cache->size >= cnt);
+
+ if (cache->count == 0) {
+ assert (is_empty_list(&cache->lru));
+ }
+ else {
+ struct util_cache_entry *header = cache->lru.next;
+
+ assert (header);
+ assert (!is_empty_list(&cache->lru));
+
+ for (i = 0; i < cache->count; i++)
+ header = header->next;
+
+ assert(header == &cache->lru);
+ }
+#endif
+
+ (void)cache;
+}
projects / mesa.git / blobdiff