[PATCH v2] hash: clarify comments for RTE_HASH_BUCKET_ENTRIES

[Honnappa Nagarahalli]

<snip>

> 
> This patch adds a comment for RTE_HASH_BUCKET_ENTRIES explaining why a
> particular value was chosen.
> 
> Signed-off-by: Vladimir Medvedkin <vladimir.medvedkin at intel.com>
Looks good
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli at arm.com>

> ---
>  lib/hash/rte_cuckoo_hash.h | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/hash/rte_cuckoo_hash.h b/lib/hash/rte_cuckoo_hash.h index
> 85be49d3bb..eb2644f74b 100644
> --- a/lib/hash/rte_cuckoo_hash.h
> +++ b/lib/hash/rte_cuckoo_hash.h
> @@ -101,7 +101,13 @@ const rte_hash_cmp_eq_t
> cmp_jump_table[NUM_KEY_CMP_CASES] = {  #endif
> 
> 
> -/** Number of items per bucket. */
> +/**
> + * Number of items per bucket.
> + * 8 is a tradeoff between performance and memory consumption.
> + * When it is equal to 8, multiple 'struct rte_hash_bucket' can be fit
> + * on a single cache line (64 or 128 bytes long) without any gaps
> + * in memory between them due to alignment.
> + */
>  #define RTE_HASH_BUCKET_ENTRIES		8
> 
>  #if !RTE_IS_POWER_OF_2(RTE_HASH_BUCKET_ENTRIES)
> --
> 2.25.1