Hello Abdullah,
        Thank you for the patch, few comments inline.

The short commit log could be changed as follows:

"lib/hash: add defer queue reclaim API”

> On Mar 2, 2024, at 3:27 PM, Abdullah Ömer Yamaç <aomeryamac@gmail.com> wrote:
>
> This patch adds a new feature to the hash library to allow the user to
> reclaim the defer queue. This is useful when the user wants to force
> reclaim resources that are not being used. This API is only available
> if the RCU is enabled.
>
> Signed-off-by: Abdullah Ömer Yamaç <aomeryamac@gmail.com>
> Acked-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Please add this only after you get an explicit Ack on the patch.

> ---
> lib/hash/rte_cuckoo_hash.c | 23 +++++++++++++++++++++++
> lib/hash/rte_hash.h        | 14 ++++++++++++++
> lib/hash/version.map       |  7 +++++++
> 3 files changed, 44 insertions(+)
>
> diff --git a/lib/hash/rte_cuckoo_hash.c b/lib/hash/rte_cuckoo_hash.c
> index 9cf94645f6..254fa80cc5 100644
> --- a/lib/hash/rte_cuckoo_hash.c
> +++ b/lib/hash/rte_cuckoo_hash.c
> @@ -1588,6 +1588,27 @@ rte_hash_rcu_qsbr_add(struct rte_hash *h, struct rte_hash_rcu_config *cfg)
> return 0;
> }
>
> +int
> +rte_hash_rcu_qsbr_dq_reclaim(struct rte_hash *h)
We need to add freed, pending and available parameters to this API. I think this information will be helpful for the users. For ex: in your use case, you could use the pending value to calculate the available hash entries.

> +{
> + int ret;
> +
> + if (h->hash_rcu_cfg == NULL || h->dq == NULL) {
We can skip NULL check for h->dq as the RCU reclaim API makes the same check.

> + rte_errno = EINVAL;
> + return -1;
> + }
> +
> + ret = rte_rcu_qsbr_dq_reclaim(h->dq, h->hash_rcu_cfg->max_reclaim_size, NULL, NULL, NULL);
> + if (ret != 0) {
> + HASH_LOG(ERR,
> + "%s: could not reclaim the defer queue in hash table",
> + __func__);
> + return -1;
> + }
> +
> + return 0;
> +}
> +
> static inline void
> remove_entry(const struct rte_hash *h, struct rte_hash_bucket *bkt,
> unsigned int i)
> diff --git a/lib/hash/rte_hash.h b/lib/hash/rte_hash.h
> index 7ecc021111..c119477d50 100644
> --- a/lib/hash/rte_hash.h
> +++ b/lib/hash/rte_hash.h
> @@ -674,6 +674,21 @@ rte_hash_iterate(const struct rte_hash *h, const void **key, void **data, uint32
>  */
> int rte_hash_rcu_qsbr_add(struct rte_hash *h, struct rte_hash_rcu_config *cfg);
>
> +/**
> + * Reclaim resources from the defer queue.
> + * This API reclaim the resources from the defer queue if rcu is enabled.
> + *
> + * @param h
> + *   the hash object to reclaim resources
> + * @return
> + *   On success - 0
> + *   On error - 1 with error code set in rte_errno.
> + *   Possible rte_errno codes are:
> + *   - EINVAL - invalid pointer or invalid rcu mode
We can remove the ‘invalid rcd mode’.

> + */
> +__rte_experimental
> +int rte_hash_rcu_qsbr_dq_reclaim(struct rte_hash *h);
> +
> #ifdef __cplusplus
> }
> #endif
> diff --git a/lib/hash/version.map b/lib/hash/version.map
> index 6b2afebf6b..cec0e8fc67 100644
> --- a/lib/hash/version.map
> +++ b/lib/hash/version.map
> @@ -48,3 +48,9 @@ DPDK_24 {
>
> local: *;
> };
> +
> +EXPERIMENTAL {
> + global:
> +
> + rte_hash_rcu_qsbr_dq_reclaim;
> +}
> \ No newline at end of file
> --
> 2.34.1
>