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[35.194.66.114]) by smtp.gmail.com with ESMTPSA id l4-20020ac84584000000b00421b14f7e7csm4356420qtn.48.2023.12.04.06.54.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 04 Dec 2023 06:54:41 -0800 (PST) Date: Mon, 04 Dec 2023 09:54:40 -0500 From: Willem de Bruijn To: Jesper Dangaard Brouer , Song Yoong Siang , "David S . Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Jonathan Corbet , Bjorn Topel , Magnus Karlsson , Maciej Fijalkowski , Jonathan Lemon , Alexei Starovoitov , Daniel Borkmann , John Fastabend , Stanislav Fomichev , Lorenzo Bianconi , Tariq Toukan , Willem de Bruijn , Maxime Coquelin , Andrii Nakryiko , Mykola Lysenko , Martin KaFai Lau , Song Liu , Yonghong Song , KP Singh , Hao Luo , Jiri Olsa , Shuah Khan , Alexandre Torgue , Jose Abreu Cc: netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, bpf@vger.kernel.org, xdp-hints@xdp-project.net, linux-stm32@st-md-mailman.stormreply.com, linux-arm-kernel@lists.infradead.org, linux-kselftest@vger.kernel.org Message-ID: <656de830e8d70_2e983e294ca@willemb.c.googlers.com.notmuch> In-Reply-To: <43b01013-e78b-417e-b169-91909c7309b1@kernel.org> References: <20231203165129.1740512-1-yoong.siang.song@intel.com> <20231203165129.1740512-3-yoong.siang.song@intel.com> <43b01013-e78b-417e-b169-91909c7309b1@kernel.org> Subject: Re: [PATCH bpf-next v3 2/3] net: stmmac: add Launch Time support to XDP ZC Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Jesper Dangaard Brouer wrote: > > > On 12/3/23 17:51, Song Yoong Siang wrote: > > This patch enables Launch Time (Time-Based Scheduling) support to XDP zero > > copy via XDP Tx metadata framework. > > > > Signed-off-by: Song Yoong Siang > > --- > > drivers/net/ethernet/stmicro/stmmac/stmmac.h | 2 ++ > > As requested before, I think we need to see another driver implementing > this. > > I propose driver igc and chip i225. > > The interesting thing for me is to see how the LaunchTime max 1 second > into the future[1] is handled code wise. One suggestion is to add a > section to Documentation/networking/xsk-tx-metadata.rst per driver that > mentions/documents these different hardware limitations. It is natural > that different types of hardware have limitations. This is a close-to > hardware-level abstraction/API, and IMHO as long as we document the > limitations we can expose this API without too many limitations for more > capable hardware. I would assume that the kfunc will fail when a value is passed that cannot be programmed. What is being implemented here already exists for qdiscs. The FQ qdisc takes a horizon attribute and " when a packet is beyond the horizon at enqueue() time: - either drop the packet (default policy) - or cap its delivery time to the horizon. " commit 39d010504e6b ("net_sched: sch_fq: add horizon attribute") Having the admin manually configure this on the qdisc based on off-line knowledge of the device is more fragile than if the device would somehow signal its limit to the stack. But I don't think we should add enforcement of that as a requirement for this xdp extension of pacing.