On Tue, Sep 06, 2016 at 08:34:01PM +0100, Pablo de Lara wrote:
> In order to optimize lookup performance, hash structure
> is reordered, so all fields used for lookup will be
> in the first cache line.
>
> Signed-off-by: Pablo de Lara <pablo.de.lara.guarch at intel.com>
> ---
> lib/librte_hash/rte_cuckoo_hash.h | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/lib/librte_hash/rte_cuckoo_hash.h
> b/lib/librte_hash/rte_cuckoo_hash.h
> index e290dab..701531a 100644
> --- a/lib/librte_hash/rte_cuckoo_hash.h
> +++ b/lib/librte_hash/rte_cuckoo_hash.h
> @@ -182,9 +182,7 @@ struct rte_hash_bucket {
>
> /** A hash table structure. */
> struct rte_hash {
> - char name[RTE_HASH_NAMESIZE]; /**< Name of the hash. */
> - uint32_t entries; /**< Total table entries. */
> - uint32_t num_buckets; /**< Number of buckets in table. */
> + /* first cache line - fields used in lookup */
> uint32_t key_len; /**< Length of hash key. */
> rte_hash_function hash_func; /**< Function used to calculate hash. */
> uint32_t hash_func_init_val; /**< Init value used by hash_func. */
> @@ -196,12 +194,13 @@ struct rte_hash {
> from hash signature. */
> uint32_t key_entry_size; /**< Size of each key entry. */
>
> - struct rte_ring *free_slots; /**< Ring that stores all indexes
> - of the free slots in the key
> table */
> void *key_store; /**< Table storing all keys and data */
> struct rte_hash_bucket *buckets; /**< Table with buckets storing
> all the
> hash values and key
> indexes
> to the key table*/
> +
> + struct rte_ring *free_slots; /**< Ring that stores all indexes
> + of the free slots in the key
> table */
> uint8_t hw_trans_mem_support; /**< Hardware transactional
> memory support */
> struct lcore_cache *local_free_slots;
> @@ -209,6 +208,9 @@ struct rte_hash {
> enum add_key_case add_key; /**< Multi-writer hash add behavior */
>
> rte_spinlock_t *multiwriter_lock; /**< Multi-writer spinlock for w/o TM
> */
> + char name[RTE_HASH_NAMESIZE]; /**< Name of the hash. */
> + uint32_t entries; /**< Total table entries. */
> + uint32_t num_buckets; /**< Number of buckets in table. */
Hi Pablo,
While I've no strong objection to the change, having the name at the start
is a common paradigm in DPDK. Rather than place these fields at the end,
can you get the same effect by just marking the key_len function
__rte_cache_aligned? It may use a little more memory per table, but given that
the size of the hash table is going to be largely governed by the table data,
I don't see an extra 64 bytes in the structure as being an issue.
Regards,
/Bruce
