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Thu, 05 Nov 2026 14:21:06 -0800 (PST) Received: from localhost ([2a03:2880:9ff:44::]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-36fa922b205sm39909eec.11.2026.11.05.14.21.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Nov 2026 14:21:06 -0800 (PST) From: Stanislav Fomichev X-Google-Original-From: Stanislav Fomichev To: netdev@vger.kernel.org Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, andrew+netdev@lunn.ch, edumazet@kernel.org, horms@kernel.org, corbet@lwn.net, skhan@linuxfoundation.org, rdunlap@infradead.org, michael.chan@broadcom.com, pavan.chebbi@broadcom.com, saeedm@nvidia.com, tariqt@nvidia.com, mbloch@nvidia.com, alexanderduyck@fb.com, kernel-team@meta.com, sdf@fomichev.me, dimitri.daskalakis1@gmail.com, almasrymina@google.com, dtatulea@nvidia.com, bobbyeshleman@meta.com, asml.silence@gmail.com, daniel@iogearbox.net, razor@blackwall.org, leitao@debian.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org, linux-kselftest@vger.kernel.org, leon@kernel.org Subject: [PATCH net-next v3 5/9] bnxt_en: set the netmem TX frag size limit to 32KB Date: Thu, 5 Nov 2026 14:20:54 -0800 Message-ID: <20261105222058.944293-6-sdf@fomichev.me> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261105222058.944293-1-sdf@fomichev.me> References: <20261105222058.944293-1-sdf@fomichev.me> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The TX BD length field is 16 bits wide. Set the netmem TX frag size limit to the largest power of 2 which fits, which keeps 4K aligned frags 4K aligned. With 4K pages this raises the PAGE_SIZE default. With 64K pages it lowers it, 64KB frags would otherwise wrap the BD length to 0 with BIG TCP. Tested on a 50Gb/s NIC: devmem TX from a 2MB hugepage-backed udmabuf runs at line rate with 2-3 frags per 64KB skb, none above 32KB. kperf output (sender side, 1 flow): client: == Source client: Tx 46.358 Gbps (174483046400 bytes in 30110590 usec) client: Rx 0.000 Gbps (0 bytes in 30110590 usec) client: TCP retrans reord rtt rttvar d_ce snd_wnd cwnd client: 729 153 599 48 0 13893632 3147 client: net CPU 71: usr: 0.03% sys: 0.06% idle:67.62% iow: 0.00% irq: 1.12% sirq:31.14% client: app CPU 72: usr: 0.16% sys: 6.01% idle:90.66% iow: 0.00% irq: 0.83% sirq: 2.32% Signed-off-by: Stanislav Fomichev Reviewed-by: Mina Almasry Reviewed-by: Michael Chan Reviewed-by: Dragos Tatulea --- drivers/net/ethernet/broadcom/bnxt/bnxt.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt.c b/drivers/net/ethernet/broadcom/bnxt/bnxt.c index e7a4190a8c78..c8a887facc20 100644 --- a/drivers/net/ethernet/broadcom/bnxt/bnxt.c +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt.c @@ -17439,6 +17439,7 @@ static int bnxt_init_one(struct pci_dev *pdev, const struct pci_device_id *ent) if (BNXT_SUPPORTS_QUEUE_API(bp)) dev->queue_mgmt_ops = &bnxt_queue_mgmt_ops; dev->netmem_tx = NETMEM_TX_DMA; + dev->netmem_tx_max_frag_size = SZ_32K; rc = register_netdev(dev); if (rc) -- 2.53.0-Meta