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Thu, 4 Nov 2021 12:49:52 -0400 (EDT) From: Thomas Monjalon <thomas@monjalon.net> To: "Medvedkin, Vladimir" <vladimir.medvedkin@intel.com> Cc: "Kinsella, Ray" <ray.kinsella@intel.com>, Syam Prasad N Pearson <syam.pearson@gadgeon.com>, "users@dpdk.org" <users@dpdk.org>, "dev@dpdk.org" <dev@dpdk.org>, "Wang, Yipeng1" <yipeng1.wang@intel.com>, "Gobriel, Sameh" <sameh.gobriel@intel.com>, "Richardson, Bruce" <bruce.richardson@intel.com> Subject: Re: [dpdk-dev] Doubt regarding DPDK hash Library implementation Date: Thu, 04 Nov 2021 17:49:51 +0100 Message-ID: <3060108.LiUVKm96O0@thomas> In-Reply-To: <6c1c908e-6a9a-c50d-0fa3-be61770ef97c@intel.com> References: <CAA2VcQjJPvz63p=gzM+Sh4J7UCRSUaHg5NBgB0o-pmq3m=kmmg@mail.gmail.com> <PH0PR11MB47769F949D7FD3273A0ABB48908D9@PH0PR11MB4776.namprd11.prod.outlook.com> <6c1c908e-6a9a-c50d-0fa3-be61770ef97c@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" X-BeenThere: users@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK usage discussions <users.dpdk.org> List-Unsubscribe: <https://mails.dpdk.org/options/users>, <mailto:users-request@dpdk.org?subject=unsubscribe> List-Archive: <http://mails.dpdk.org/archives/users/> List-Post: <mailto:users@dpdk.org> List-Help: <mailto:users-request@dpdk.org?subject=help> List-Subscribe: <https://mails.dpdk.org/listinfo/users>, <mailto:users-request@dpdk.org?subject=subscribe> Errors-To: users-bounces@dpdk.org 04/11/2021 17:39, Medvedkin, Vladimir: > >> 01/11/2021 11:55, Syam Prasad N Pearson: > >>> /** Number of items per bucket. */ > >>> *#define RTE_HASH_BUCKET_ENTRIES 8* > >>> > >>> defined inside: > >>> dpdk-20.11.3/dpdk-stable-20.11.3/lib/librte_hash /rte_cuckoo_hash.h > >>> > >>> Why does the library take this value as *8*, is there any particular > >>> reason for this? what if it is 16,32... etc. > > Yes, RTE_HASH_BUCKET_ENTRIES can be any power of 2. > The reason for choosing 8 is a tradeoff between performance and memory. > When it is equal to 8, the sizeof(struct rte_hash_bucket) equal to > RTE_CACHE_LINE_SIZE, thus, there are no gaps in memory between the hash > buckets due to their alignment. That's a good comment to add in the code.