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[204.195.96.226]) by smtp.gmail.com with ESMTPSA id a92af1059eb24-13b2ab0fc3fsm8914818c88.2.2026.06.30.06.39.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 30 Jun 2026 06:39:19 -0700 (PDT) Date: Tue, 30 Jun 2026 06:39:15 -0700 From: Stephen Hemminger To: Maxime Leroy Cc: dev@dpdk.org, hemant.agrawal@nxp.com, sachin.saxena@nxp.com, mb@smartsharesystems.com Subject: Re: [PATCH] net/dpaa2: drop the fake software VLAN strip offload Message-ID: <20260630063915.516fef48@phoenix.local> In-Reply-To: <20260630124945.399268-1-maxime@leroys.fr> References: <20260630124945.399268-1-maxime@leroys.fr> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable 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, 30 Jun 2026 14:49:45 +0200 Maxime Leroy wrote: > posts to the store buffer while the line fills in the background, and > the rewritten fields are forwarded straight from there. buf_addr has > nothing to forward, so it must be read from the line, whose fill is > still in flight, and the read stalls. The ethertype read that follows, > on the cold payload line, stalls again. Read later by the application, > when the fill has completed, the same read hits. The offload just > performs it at the worst possible moment. >=20 > Measured on a single-core port-to-port forwarding test over two 10G > ports (one core at 2 GHz, 64-byte untagged frames): >=20 > - throughput 4.22 -> 5.00 Mpps (+18 percent) > - IPC 0.93 -> 1.25: the cost was memory stall, not compute > - L3/DRAM-bound L2 refills 319M -> 200M over 10s (-37 percent) >=20 > perf confirms it: with the offload, the buf_addr load (the cold mbuf > field) and the payload load account for about 84 percent of the Rx > burst's L2 refills; removing it, those vanish and only the inherent DQRR > dequeue misses remain. >=20 > Stop advertising VLAN_STRIP and remove the rte_vlan_strip() calls from > every Rx path. This is a behavioural change: the tag is left in the > frame, so an application must strip it itself, on the L2 header it > already reads. >=20 > Signed-off-by: Maxime Leroy > Acked-by: Morten Br=C3=B8rup > Acked-by: Stephen Hemminger > Acked-by: Hemant Agrawal Applied to next-net