Re: [PATCH v5] lib/hash: add defer queue reclaim API

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

Hi Abdullah,
        This looks good, except for one comment inline.

> On Apr 27, 2024, at 2:54 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>
> ---
> app/test/test_hash.c       | 90 ++++++++++++++++++++++++++++++++++++++
> lib/hash/rte_cuckoo_hash.c | 21 +++++++++
> lib/hash/rte_hash.h        | 25 +++++++++++
> lib/hash/version.map       |  7 +++
> 4 files changed, 143 insertions(+)
>
> diff --git a/app/test/test_hash.c b/app/test/test_hash.c
> index d586878a22..e763d0503f 100644
> --- a/app/test/test_hash.c
> +++ b/app/test/test_hash.c
> @@ -2183,6 +2183,93 @@ test_hash_rcu_qsbr_sync_mode(uint8_t ext_bkt)
>
> }
>
> +/*
> + * rte_hash_rcu_qsbr_dq_reclaim unit test.
> + */
> +static int test_hash_rcu_qsbr_dq_reclaim(void)
> +{
> + size_t sz;
> + int32_t status;
> + unsigned int total_entries = 8;
> + unsigned int freed, pending, available;
> + uint32_t reclaim_keys[8] = {10, 11, 12, 13, 14, 15, 16, 17};
> + struct rte_hash_rcu_config rcu_cfg = {0};
> + struct rte_hash_parameters hash_params = {
> +    .name = "test_hash_rcu_qsbr_dq_reclaim",
> +    .entries = total_entries,
> +    .key_len = sizeof(uint32_t),
> +    .hash_func = NULL,
> +    .hash_func_init_val = 0,
> +    .socket_id = 0,
> + };
> +
> + hash_params.extra_flag = RTE_HASH_EXTRA_FLAGS_RW_CONCURRENCY_LF;
> +
> + g_qsv = NULL;
> + g_handle = NULL;
> +
> + printf("\n# Running RCU QSBR DQ mode, reclaim defer queue functional test\n");
> +
> + g_handle = rte_hash_create(&hash_params);
> + RETURN_IF_ERROR_RCU_QSBR(g_handle == NULL, "Hash creation failed");
> +
> + /* Create RCU QSBR variable */
> + sz = rte_rcu_qsbr_get_memsize(RTE_MAX_LCORE);
> + g_qsv = (struct rte_rcu_qsbr *)rte_zmalloc_socket(NULL, sz, RTE_CACHE_LINE_SIZE,
> +  SOCKET_ID_ANY);
> + RETURN_IF_ERROR_RCU_QSBR(g_qsv == NULL, "RCU QSBR variable creation failed");
> +
> + status = rte_rcu_qsbr_init(g_qsv, RTE_MAX_LCORE);
> + RETURN_IF_ERROR_RCU_QSBR(status != 0, "RCU QSBR variable initialization failed");
> +
> + rcu_cfg.v = g_qsv;
> + rcu_cfg.dq_size = total_entries;
> + rcu_cfg.mode = RTE_HASH_QSBR_MODE_DQ;
> +
> + /* Attach RCU QSBR to hash table */
> + status = rte_hash_rcu_qsbr_add(g_handle, &rcu_cfg);
> + RETURN_IF_ERROR_RCU_QSBR(status != 0, "Attach RCU QSBR to hash table failed");
> +
> + /* Register pseudo reader */
> + status = rte_rcu_qsbr_thread_register(g_qsv, 0);
> + RETURN_IF_ERROR_RCU_QSBR(status != 0, "RCU QSBR thread registration failed");
> + rte_rcu_qsbr_thread_online(g_qsv, 0);
> +
> + /* Fill half of the hash table */
> + for (size_t i = 0; i < total_entries / 2; i++)
> + status = rte_hash_add_key(g_handle, &reclaim_keys[i]);
> +
> + /* Lookup inserted elements*/
> + for (size_t i = 0; i < total_entries / 2; i++)
> + rte_hash_lookup(g_handle, &reclaim_keys[i]);
Why do we need to lookup the entries?

> +
> + /* Try to put these elements into the defer queue*/
> + for (size_t i = 0; i < total_entries / 2; i++)
> + rte_hash_del_key(g_handle, &reclaim_keys[i]);
> +
> + /* Reader quiescent */
> + rte_rcu_qsbr_quiescent(g_qsv, 0);
> +
> + status = rte_hash_add_key(g_handle, &reclaim_keys[0]);
> + RETURN_IF_ERROR_RCU_QSBR(status < 0, "failed to add key (pos[%u]=%d)", 0, status);
> +
> + /* This should be (total_entries / 2) + 1 (last add) */
> + unsigned int hash_size = rte_hash_count(g_handle);
> +
> + /* Freed size should be (total_entries / 2) */
> + rte_hash_rcu_qsbr_dq_reclaim(g_handle, &freed, &pending, &available);
> +
> + rte_hash_free(g_handle);
> + rte_free(g_qsv);
> +
> + if (hash_size != (total_entries / 2 + 1) || freed != (total_entries / 2)) {
> + printf("Failed to reclaim defer queue\n");
> + return -1;
> + }
> +
> + return 0;
> +}
> +
> /*
> * Do all unit and performance tests.
> */
> @@ -2261,6 +2348,9 @@ test_hash(void)
> if (test_hash_rcu_qsbr_sync_mode(1) < 0)
> return -1;
>
> + if (test_hash_rcu_qsbr_dq_reclaim() < 0)
> + return -1;
> +
> return 0;
> }
>
> diff --git a/lib/hash/rte_cuckoo_hash.c b/lib/hash/rte_cuckoo_hash.c
> index 9cf94645f6..52ccada12a 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, unsigned int *freed, unsigned int *pending,
> + unsigned int *available)
> +{
> + int ret;
> +
> + if (h == NULL || h->hash_rcu_cfg == NULL) {
> + HASH_LOG(ERR, "Invalid input parameter");
> + rte_errno = EINVAL;
> + return 1;
> + }
> +
> + ret = rte_rcu_qsbr_dq_reclaim(h->dq, h->hash_rcu_cfg->max_reclaim_size, freed, pending,
> +      available);
> + 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..e1e0375fd5 100644
> --- a/lib/hash/rte_hash.h
> +++ b/lib/hash/rte_hash.h
> @@ -674,6 +674,31 @@ 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.
> + * @param freed
> + *   Number of resources that were freed.
> + * @param pending
> + *   Number of resources pending on the defer queue.
> + *   This number might not be accurate if multi-thread safety is configured.
> + * @param available
> + *   Number of resources that can be added to the defer queue.
> + *   This number might not be accurate if multi-thread safety is configured.
> + * @return
> + *   On success - 0
> + *   On error - 1 with error code set in rte_errno.
> + *   Possible rte_errno codes are:
> + *   - EINVAL - invalid pointer
> + */
> +__rte_experimental
> +int rte_hash_rcu_qsbr_dq_reclaim(struct rte_hash *h, unsigned int *freed,
> +    unsigned int *pending,
> +    unsigned int *available);
> +
> #ifdef __cplusplus
> }
> #endif
> diff --git a/lib/hash/version.map b/lib/hash/version.map
> index 6f4bcdb71b..d348dd9196 100644
> --- a/lib/hash/version.map
> +++ b/lib/hash/version.map
> @@ -53,3 +53,10 @@ INTERNAL {
> rte_thash_gfni_stub;
> rte_thash_gfni_bulk_stub;
> };
> +
> +EXPERIMENTAL {
> + global:
> +
> + # added in 24.07
> + rte_hash_rcu_qsbr_dq_reclaim;
> +};
> --
> 2.34.1
>

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