generic/lru: evictions counter to aid efficiency prediction

lib/generic/lru.h

@@ -88,6 +88,7 @@ typedef void (*lru_free_f)(void *baton, void *ptr);
 /** @brief LRU structure base. */
 #define lru_hash_struct \
 	uint32_t size;      /**< Number of slots */ \
+	uint32_t evictions; /**< Number of evictions. */ \
 	uint32_t stride;    /**< Stride of the 'slots' array */ \
 	lru_free_f evict;   /**< Eviction function */ \
 	void *baton;        /**< Passed to eviction function */
@@ -107,6 +108,18 @@ struct { \
 	} slots[]; \
 }
 
+/** Get slot at given index. */
+static inline void *lru_slot_at(struct lru_hash_base *lru, uint32_t id)
+{
+	return (struct lru_slot *)(lru->slots + (id * lru->stride));
+}
+
+/** Get pointer to slot value. */
+static inline void *lru_slot_val(struct lru_slot *slot, size_t offset)
+{
+	return ((char *)slot) + offset;
+}
+
 /** @internal Slot data getter */
 static inline void *lru_slot_get(struct lru_hash_base *lru, const char *key, uint32_t len, size_t offset)
 {
@@ -114,9 +127,9 @@ static inline void *lru_slot_get(struct lru_hash_base *lru, const char *key, uin
 		return NULL;
 	}
 	uint32_t id = hash(key, len) % lru->size;
-	struct lru_slot *slot = (struct lru_slot *)(lru->slots + (id * lru->stride));
+	struct lru_slot *slot = lru_slot_at(lru, id);
 	if (lru_slot_match(slot, key, len)) {
-		return ((char *)slot) + offset;
+		return lru_slot_val(slot, offset);
 	}
 	return NULL;
 }
@@ -128,12 +141,13 @@ static inline void *lru_slot_set(struct lru_hash_base *lru, const char *key, uin
 		return NULL;
 	}
 	uint32_t id = hash(key, len) % lru->size;
-	struct lru_slot *slot = (struct lru_slot *)(lru->slots + (id * lru->stride));
+	struct lru_slot *slot = lru_slot_at(lru, id);
 	if (!lru_slot_match(slot, key, len)) {
 		if (slot->key) {
+			lru->evictions += 1;
 			free(slot->key);
 			if (lru->evict) {
-				lru->evict(lru->baton, ((char *)slot) + offset);
+				lru->evict(lru->baton, lru_slot_val(slot, offset));
 			}
 		}
 		memset(slot, 0, lru->stride);
@@ -144,7 +158,7 @@ static inline void *lru_slot_set(struct lru_hash_base *lru, const char *key, uin
 		memcpy(slot->key, key, len);
 		slot->len = len;
 	}
-	return ((char *)slot) + offset;
+	return lru_slot_val(slot, offset);
 }
 
 /**