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Wed, 11 Nov 2026 13:52:14 -0800 (PST) Received: from localhost ([2a03:2880:9ff:44::]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-37520bf3e18sm38761082eec.16.2026.11.11.13.52.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 11 Nov 2026 13:52:13 -0800 (PST) Date: Wed, 11 Nov 2026 13:50:20 -0800 From: Stanislav Fomichev To: Jakub Kicinski Cc: netdev@vger.kernel.org, davem@davemloft.net, edumazet@google.com, 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, narcisav.kernel@gmail.com Subject: Re: [PATCH net-next v3 4/9] net: devmem: add a per-device netmem TX frag size limit Message-ID: References: <20261105222058.944293-1-sdf@fomichev.me> <20261105222058.944293-5-sdf@fomichev.me> <20261110143615.05f9adbd@kernel.org> X-Mailing-List: netdev@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20261110143615.05f9adbd@kernel.org> On 11/10, Jakub Kicinski wrote: > On Thu, 5 Nov 2026 14:20:53 -0800 Stanislav Fomichev wrote: > > Devmem TX frags are bounded only by the net_iov size, which is about > > to grow up to 2MB, more than some devices can describe in a single TX > > descriptor. > > How is this different than normal zerocopy Tx? > Drivers already have to deal with long frags. > Having partially applicable limit seems like a bad idea. Thanks for the pointers. Yes, looks like I can drop all this per-frag enforcement. But bnxt is still broken with bigtcp, will try to hack on something separately (queue stats/etc to make it actually run tso.py).. CC'd Narcisa (synced offline), unless your priorities change and you get there first (or I get carried away by something else)..