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[204.195.96.226]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-327f9209fafsm62621928eec.23.2026.08.25.07.15.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 25 Aug 2026 07:15:05 -0700 (PDT) Date: Tue, 25 Aug 2026 07:14:55 -0700 From: Stephen Hemminger To: Maxime Leroy Cc: Hemant Agrawal , Sachin Saxena , dev@dpdk.org Subject: Re: [PATCH v3] net/dpaa2: hash inner IP for tunnelled traffic Message-ID: <20260825071455.4bc37db0@phoenix.local> In-Reply-To: <20260825074255.367302-1-maxime@leroys.fr> References: <20260723093540.1839619-1-maxime@leroys.fr> <20260825074255.367302-1-maxime@leroys.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org On Tue, 25 Aug 2026 09:42:55 +0200 Maxime Leroy wrote: > The RSS key only extracted the outer IP header. Tunnelled traffic whose > outer headers are fixed then carries no entropy for the hash, so every > flow lands on a single Rx queue. > > Extract both the outer IP (header index 0) and the innermost IP instance > (HDR_INDEX_LAST). Plain frames keep being hashed on their only IP header; > the inner extract resolves to nothing and adds no entropy. Tunnelled > frames are also hashed on their inner IP and spread across the Rx queues. > > That a lone IP header does not resolve HDR_INDEX_LAST is the regression > reverted by commit 2b375df07e48 ("net/dpaa2: revert inner RSS level > support"): extracted only at HDR_INDEX_LAST, every plain frame hashed to > the same value and landed on one Rx queue. > > The worst case, requesting every type the PMD advertises, is 16 extracts > out of the DPKG_MAX_NUM_OF_EXTRACTS 20. On LX2160A > dpni_set_rx_hash_dist() accepts the key, and plain IPv4, plain IPv6, VLAN > tagged and tunnelled IPv6 traffic all spread across the Rx queues. > > This is the PMD default hash: dpaa2 does not expose the ethdev RSS level > selector, so it applies to every RSS request. The hardware cannot hash > the inner IP alone, as HDR_INDEX_LAST only resolves when several IP > headers are stacked and a plain frame would hash to a constant. Folding > the outer IP into the key is therefore unavoidable, and two tunnelled > flows that share an inner IP but differ in their outer IP may hash to > different queues. This is documented in the dpaa2 guide. > > Signed-off-by: Maxime Leroy > --- Applied to next-net