From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=BAYES_00,DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED,DKIM_VALID,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id EEF7AC433E0 for ; Sun, 31 Jan 2021 09:27:47 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 4BCF064E11 for ; Sun, 31 Jan 2021 09:27:47 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4BCF064E11 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=gMK7+BWRabYIjgHuqGhrpVzbnF1JY0Xh2pgvVNMz880=; b=m3soq5SGEpyx37/fF09j6+Igf 3ky9Ec60PBSEG0uRtOKDD7CvVKCtAIjHVbDfDm+O3bhQg4CeAoj7KT1U7a53fxCjFZKeBoiM9ivad obyklKBTYWUu3Rr97E/z9XtivOs/pT7TB9vjAbEct6H32eiq0fgUm7Z+KT3qQg3NbWRNPDlAA8unT KvRnX/6fnV2UyXHFQx9jTNoSkubFYAruInbukXURrAFcGla76jWixmkJtT769zrAy953/FN8Tj5BQ h96KPGsXOVf8663zENVfL3l8FESXwe84JSMnXY3YsCLPJZSu2W/6tZM3Wwt8+EzUmFS+YdfUiyaB6 aeZExGWwA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l6918-0001F2-IV; Sun, 31 Jan 2021 09:27:38 +0000 Received: from mail-ej1-x62c.google.com ([2a00:1450:4864:20::62c]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1l6915-0001Ei-3Z for linux-nvme@lists.infradead.org; Sun, 31 Jan 2021 09:27:35 +0000 Received: by mail-ej1-x62c.google.com with SMTP id g12so19492850ejf.8 for ; Sun, 31 Jan 2021 01:27:34 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=DQuz1pa9GvbRd37vkQ2NVh0PZw3uNiGrjR2cuG/k2HM=; b=iSxoOmK/bHvymVhs7lEGzAKWPsXzqb96+fBQfcqEz7TWjaRPk/F9y/jNqZmVOM7azD uW9kLQidLFRP8nuTbveE+8KZMrFwHiIIeGTE61I1UCAiK4nu70RoMDE83i9WE8WMpAEp gBeiKmW06lxxXm/jmyfoggAgPtmQKPOBh1Pw3+rgmmE71Z3TzJNljhxO2QbPJo5uImCk T+UQL8TwdO+B3XivVvGloYo64c5tBzJX43OSe3J9RgJEqFMZ9H+Aw/9uFfmygqC9gwSB W9OeVyU2c781b1XM/Ve84o2nR4xUE87cnXqbXk6NRtdo5rWRki7SSSszLTtTtm9QXuJ0 MLug== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=DQuz1pa9GvbRd37vkQ2NVh0PZw3uNiGrjR2cuG/k2HM=; b=LA5KDlZPJ1Z0rHvSm7w9WApHdLsNgZzzerSTd9NKhZVKGRdT26B8InSKAoRwsCrX/P 7KLtt2qGqkDei4EjUE+57rJznmrLDxiFZi7xn6TEfYR93/sM2iHKKHX6EgPX9WUav6yP 0MuHjFt1Tt4ZjeAqZR+D7413Phdr6fLWCU0hln7Ii3i2iRtgv/ZUw16aXmmGgxc8PZfX bHMeDGzz8nGsA5tbD3MTnU9MhDAEYcoAomvdyNzgYtE5sQs8OYe8O/RzLVIRMBAe3ksM yC4wP7DvlsRstbwX14D8q1b/3ILHTclMnyo7phb/32NrA9l064F3FmnO8EAvukS9Lwpl 5KcQ== X-Gm-Message-State: AOAM533vANUBizv2zqkD389Cr6V6YSHrNZ7xrMkJOdd/LW9cuzI3eImY l3/KLJ9td3/ttzbDYSV9IGk= X-Google-Smtp-Source: ABdhPJxEegalHxQS/egMrax4TUygJ9kqmPPYFJMTrCxpod0Wg/kZYUvmjVWfXpHsq8edhR3KRWHGZg== X-Received: by 2002:a17:906:a149:: with SMTP id bu9mr12692150ejb.185.1612085253859; Sun, 31 Jan 2021 01:27:33 -0800 (PST) Received: from [132.68.43.126] ([132.68.43.126]) by smtp.gmail.com with ESMTPSA id r22sm6983019edp.9.2021.01.31.01.27.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 31 Jan 2021 01:27:33 -0800 (PST) Subject: Re: [PATCH v2 net-next 19/21] net/mlx5e: NVMEoTCP, data-path for DDP offload To: David Ahern , Boris Pismenny , kuba@kernel.org, davem@davemloft.net, saeedm@nvidia.com, hch@lst.de, sagi@grimberg.me, axboe@fb.com, kbusch@kernel.org, viro@zeniv.linux.org.uk, edumazet@google.com, smalin@marvell.com References: <20210114151033.13020-1-borisp@mellanox.com> <20210114151033.13020-20-borisp@mellanox.com> <10c28b01-49e5-c512-8670-bf8332b24b1b@gmail.com> <15248743-82bf-4283-d8c6-99f2210e42ae@gmail.com> <2a0bfce0-6226-7b9a-95b1-15f4f1f321e8@gmail.com> From: Boris Pismenny Message-ID: Date: Sun, 31 Jan 2021 11:27:31 +0200 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.1 MIME-Version: 1.0 In-Reply-To: <2a0bfce0-6226-7b9a-95b1-15f4f1f321e8@gmail.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210131_042735_192217_99B21EDE X-CRM114-Status: GOOD ( 17.52 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Yoray Zack , yorayz@nvidia.com, boris.pismenny@gmail.com, benishay@nvidia.com, linux-nvme@lists.infradead.org, netdev@vger.kernel.org, Or Gerlitz , ogerlitz@nvidia.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On 19/01/2021 6:36, David Ahern wrote: > On 1/17/21 1:42 AM, Boris Pismenny wrote: >> This is needed for a few reasons that are explained in detail >> in the tcp-ddp offload documentation. See patch 21 overview >> and rx-data-path sections. Our reasons are as follows: > > I read the documentation patch, and it does not explain it and really > should not since this is very mlx specific based on the changes. > Different h/w will have different limitations. Given that, it would be > best to enhance the patch description to explain why these gymnastics > are needed for the skb. > The text in the documentation that describes this trade-off: ''We remark that a single TCP packet may have numerous PDUs embedded inside. NICs can choose to offload one or more of these PDUs according to various trade-offs. Possibly, offloading such small PDUs is of little value, and it is better to leave it to software. `` Indeed, different HW may have other additional trade-offs. But, I suspect that this one will be important for all. >> 1) Each SKB may contain multiple PDUs. DDP offload doesn't operate on >> PDU headers, so these are written in the receive ring. Therefore, we >> need to rebuild the SKB to account for it. Additionally, due to HW >> limitations, we will only offload the first PDU in the SKB. > > Are you referring to LRO skbs here? I can't imagine going through this > for 1500 byte packets that have multiple PDUs. > > No, that is true for any skb, and non-LRO skbs in particular. Most SKBs do not contain multiple PDUs, but the ones that do are handled gracefully in this function. _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme