[PATCH v4] lib/hash: add defer queue reclaim API

["Abdullah Ömer Yamaç" <aomeryamac@gmail.com>]

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       | 97 ++++++++++++++++++++++++++++++++++++++
 lib/hash/rte_cuckoo_hash.c | 23 +++++++++
 lib/hash/rte_hash.h        | 24 ++++++++++
 lib/hash/version.map       |  7 +++
 4 files changed, 151 insertions(+)

diff --git a/app/test/test_hash.c b/app/test/test_hash.c
index d586878a22..ebeda8c322 100644
--- a/app/test/test_hash.c
+++ b/app/test/test_hash.c
@@ -2183,6 +2183,100 @@ 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]);
+
+	/* 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 +2355,9 @@ 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..4a44aadd9a 100644
--- a/lib/hash/rte_cuckoo_hash.c
+++ b/lib/hash/rte_cuckoo_hash.c
@@ -1588,6 +1588,29 @@ 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) {
+		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..edfa262aca 100644
--- a/lib/hash/rte_hash.h
+++ b/lib/hash/rte_hash.h
@@ -674,6 +674,30 @@ 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