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([2a0d:3344:5521:6b10:58fd:68f:7756:389d]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-493e0f40912sm123922735e9.4.2026.07.08.03.50.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 08 Jul 2026 03:50:10 -0700 (PDT) Message-ID: <15e72c82-ca99-481b-bd53-744fabd503b0@redhat.com> Date: Wed, 8 Jul 2026 12:50:07 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next v4 1/3] net: devmem: allow rx-buf-size > PAGE_SIZE per dmabuf binding To: Mina Almasry , Bobby Eshleman Cc: Donald Hunter , Jakub Kicinski , "David S. Miller" , Eric Dumazet , Simon Horman , Andrew Lunn , Gerd Hoffmann , Vivek Kasireddy , Sumit Semwal , =?UTF-8?Q?Christian_K=C3=B6nig?= , Shuah Khan , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org, linux-kselftest@vger.kernel.org, sdf@fomichev.me, razor@blackwall.org, daniel@iogearbox.net, matttbe@kernel.org, skhawaja@google.com, dw@davidwei.uk, Joe Damato , Bobby Eshleman References: <20260701-tcpdm-large-niovs-v4-0-ca4654f37570@meta.com> <20260701-tcpdm-large-niovs-v4-1-ca4654f37570@meta.com> From: Paolo Abeni Content-Language: en-US In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 7/7/26 10:36 PM, Mina Almasry wrote: > On Wed, Jul 1, 2026 at 12:22 PM Bobby Eshleman wrote: >> >> From: Bobby Eshleman >> >> Every devmem dmabuf binding today hands the page_pool PAGE_SIZE niovs. >> This caps a single RX descriptor at PAGE_SIZE, burning CPU on buffer >> churn for large flows. >> >> Add a bind-time netlink attribute, NETDEV_A_DMABUF_RX_BUF_SIZE, that >> lets userspace request a larger niov size. The value must be a power of >> two >= PAGE_SIZE. >> >> Measurements >> ------------ Checkpatch complains about this separator usage: ERROR: Invalid commit separator - some tools may have problems applying this #15: ------------ Please replace or remove it in the next revision >> @@ -90,16 +90,17 @@ net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding) >> struct dmabuf_genpool_chunk_owner *owner; >> unsigned long dma_addr; >> struct net_iov *niov; >> - ssize_t offset; >> - ssize_t index; >> + size_t offset; >> + size_t index; >> > > nit: I would keep this signed. Some of the most frustrating issues I > ran into is some of the underflowing and then passing a > check or > something. Although if the LLM is not complaining about this > particular case, there is probably no issue with it. I also notice a > lot of existing code that deals with indexes and offsets goes for > signed. At very least the above change should go in a separate patch, as is quite unrelated from the rest. /P