>-----Original Message----- >From: Honnappa Nagarahalli [mailto:[email protected]] >Sent: Tuesday, June 25, 2019 2:15 PM >To: Wang, Yipeng1 <[email protected]>; Gobriel, Sameh ><[email protected]>; Richardson, Bruce ><[email protected]>; De Lara Guarch, Pablo ><[email protected]>; [email protected] >Cc: [email protected]; [email protected]; [email protected]; [email protected]; >[email protected] >Subject: [PATCH 1/3] lib/hash: use ordered loads only if signature matches > >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. [Wang, Yipeng] add: This commit improves lookup performance. > >Fixes: e605a1d36 ("hash: add lock-free r/w concurrency") >Cc: [email protected] > >Signed-off-by: Honnappa Nagarahalli <[email protected]> >Reviewed-by: Gavin Hu <[email protected]> >Tested-by: Ruifeng Wang <[email protected]> >--- > 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. >+ */ [Wang, Yipeng] A bit more explanation would be helpful for future understanding of the code: "Signature comparison is done ... performance. Although this could accidentally cause the reader to read an old signature while the key_idx is updated to a new key's, any false positive will be .... of the key."
Otherwise: Acked-by: Yipeng Wang <[email protected]>
