>-----Original Message----- >From: Honnappa Nagarahalli [mailto:honnappa.nagaraha...@arm.com] >Sent: Tuesday, June 25, 2019 2:15 PM >To: Wang, Yipeng1 <yipeng1.w...@intel.com>; Gobriel, Sameh ><sameh.gobr...@intel.com>; Richardson, Bruce ><bruce.richard...@intel.com>; De Lara Guarch, Pablo ><pablo.de.lara.gua...@intel.com>; honnappa.nagaraha...@arm.com >Cc: gavin...@arm.com; ruifeng.w...@arm.com; dev@dpdk.org; n...@arm.com; >sta...@dpdk.org >Subject: [PATCH 3/3] lib/hash: adjust tbl_chng_cnt position > >tbl_chng_cnt is one of the first elements of the structure used in >the lookup. Move it to the beginning of the cache line to gain >performance. > >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.h | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > >diff --git a/lib/librte_hash/rte_cuckoo_hash.h >b/lib/librte_hash/rte_cuckoo_hash.h >index fb19bb27d..af6451b5c 100644 >--- a/lib/librte_hash/rte_cuckoo_hash.h >+++ b/lib/librte_hash/rte_cuckoo_hash.h >@@ -170,7 +170,9 @@ struct rte_hash { > > /* Fields used in lookup */ > >- uint32_t key_len __rte_cache_aligned; >+ uint32_t *tbl_chng_cnt __rte_cache_aligned; >+ /**< Indicates if the hash table changed from last read. */ >+ uint32_t key_len; > /**< Length of hash key. */ > uint8_t hw_trans_mem_support; > /**< If hardware transactional memory is used. */ >@@ -218,8 +220,6 @@ struct rte_hash { > * is piggy-backed to freeing of the key index. > */ > uint32_t *ext_bkt_to_free; >- uint32_t *tbl_chng_cnt; >- /**< Indicates if the hash table changed from last read. */ > } __rte_cache_aligned; > > struct queue_node { >-- >2.17.1
[Wang, Yipeng] I am not sure about this change. By moving counter to front, I think you seems push key_store out of the cache line. And key_store Is also used in lookup (and more commonly). My tests also show perf drop in many cases.
