Relaxed signature comparison is done first. Further ordered loads
are done only if the signature matches. Any false positives are
caught by the full key comparison.
Fixes: e605a1d36 ("hash: add lock-free r/w concurrency")
Cc: sta...@dpdk.org
Signed-off-by: Honnappa Nagarahalli <honnappa.nagaraha...@arm.com>
Reviewed-by: Gavin Hu <gavin...@arm.com>
Tested-by: Ruifeng Wang <ruifeng.w...@arm.com>
---
lib/librte_hash/rte_cuckoo_hash.c | 35 ++++++++++++++++++-------------
1 file changed, 21 insertions(+), 14 deletions(-)
diff --git a/lib/librte_hash/rte_cuckoo_hash.c
b/lib/librte_hash/rte_cuckoo_hash.c
index 953928f27..f37f6957d 100644
--- a/lib/librte_hash/rte_cuckoo_hash.c
+++ b/lib/librte_hash/rte_cuckoo_hash.c
@@ -1188,22 +1188,29 @@ search_one_bucket_lf(const struct rte_hash *h, const
void *key, uint16_t sig,
struct rte_hash_key *k, *keys = h->key_store;
for (i = 0; i < RTE_HASH_BUCKET_ENTRIES; i++) {
- key_idx = __atomic_load_n(&bkt->key_idx[i],
+ /* Signature comparison is done before the acquire-load
+ * of the key index to achieve better performance.
+ * Any false positives will be caught in full comparison
+ * of the key.
+ */
+ if (bkt->sig_current[i] == sig) {
+ key_idx = __atomic_load_n(&bkt->key_idx[i],
__ATOMIC_ACQUIRE);
- if (bkt->sig_current[i] == sig && key_idx != EMPTY_SLOT) {
- k = (struct rte_hash_key *) ((char *)keys +
- key_idx * h->key_entry_size);
- pdata = __atomic_load_n(&k->pdata,
- __ATOMIC_ACQUIRE);
+ if (key_idx != EMPTY_SLOT) {
+ k = (struct rte_hash_key *) ((char *)keys +
+ key_idx * h->key_entry_size);
+ pdata = __atomic_load_n(&k->pdata,
+ __ATOMIC_ACQUIRE);
- if (rte_hash_cmp_eq(key, k->key, h) == 0) {
- if (data != NULL)
- *data = pdata;
- /*
- * Return index where key is stored,
- * subtracting the first dummy index
- */
- return key_idx - 1;
+ if (rte_hash_cmp_eq(key, k->key, h) == 0) {
+ if (data != NULL)
+ *data = pdata;
+ /*
+ * Return index where key is stored,
+ * subtracting the first dummy index
+ */
+ return key_idx - 1;
+ }
}
}
}
--
2.17.1
