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 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4CE3AC433F5 for ; Mon, 14 Mar 2022 01:35:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:MIME-Version:References:In-Reply-To:Message-ID:Subject:Cc:To: From:Date:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=la8M+n6yVY2tNzt2OtZpWZLCEQiw6qEsmP/hCq2zD/4=; b=5Dc7G9zS9xD+QtMU35FXA2KWBI lD3VvwHTP6OTOP0Mp1gJcl4byWRR+BpkqQWg5FUlF1e5spywWR4wWsEorY0Ta6jAjPVYYfVBGgphc KldbQZNHAb0zCmSJO1E5SY9ZLr3XgZS/PpeRD1H7FArxx3PLoiVHYYmPFgr0hL5N4MIe4KHXmjtDW 1IqzTtIvXy5oZR2VE3SFT4EiBEengxu/8vIqC1hJgyLAWybwd4ay5NH0kCUcLnsjpNo8KXyM4VU5B Sv0etjtFKq3zncszDWPDaO6EoPYjwd2QuMsryvzB+UrVIx4hh4NnZ4JZCgxr+UoHZAOsAQXqX5HPH a84nNk6A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nTZbs-003ZUy-WD; Mon, 14 Mar 2022 01:34:57 +0000 Received: from smtprz01.163.net ([106.3.154.234] helo=smtp.tom.com) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1nTZbo-003ZTC-CG for linux-nvme@lists.infradead.org; Mon, 14 Mar 2022 01:34:54 +0000 Received: from localhost (localhost [127.0.0.1]) by vip-app02.163.net (Postfix) with ESMTP id 8A99D4400C7 for ; Mon, 14 Mar 2022 09:34:36 +0800 (CST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=tom.com; s=mail; t=1647221676; bh=tCwCTuNV8vbPzPftdhc6YfcqI53uXHjpEfLiz8JtAFs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=qlNPI38Ru5megsySz0hlqi5dFvTo1d09355Ft149OqY9Tp8XbttvFcby18ciqCCdB qPut456z4j2INeNoL+Fb/c9tJA9y9mnpwEMWJJsSoR/WhZHj2xOoxX89BMAI7lP7ZW jtiH7M/pbQ9Bqj+xichUzNuZFsxsvGmTV+yRynVg= Received: from localhost (HELO smtp.tom.com) ([127.0.0.1]) by localhost (TOM SMTP Server) with SMTP ID -741027541 for ; Mon, 14 Mar 2022 09:34:36 +0800 (CST) X-Virus-Scanned: Debian amavisd-new at mxtest.tom.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=tom.com; s=mail; t=1647221676; bh=tCwCTuNV8vbPzPftdhc6YfcqI53uXHjpEfLiz8JtAFs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=qlNPI38Ru5megsySz0hlqi5dFvTo1d09355Ft149OqY9Tp8XbttvFcby18ciqCCdB qPut456z4j2INeNoL+Fb/c9tJA9y9mnpwEMWJJsSoR/WhZHj2xOoxX89BMAI7lP7ZW jtiH7M/pbQ9Bqj+xichUzNuZFsxsvGmTV+yRynVg= Received: from localhost (unknown [101.93.196.13]) by antispamvip.163.net (Postfix) with ESMTPA id 96EAA154146C; Mon, 14 Mar 2022 09:34:29 +0800 (CST) Date: Mon, 14 Mar 2022 09:34:29 +0800 From: Mingbao Sun To: Sagi Grimberg Cc: Keith Busch , Jens Axboe , Christoph Hellwig , Chaitanya Kulkarni , linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org, Eric Dumazet , "David S . Miller" , Hideaki YOSHIFUJI , David Ahern , Jakub Kicinski , netdev@vger.kernel.org, tyler.sun@dell.com, ping.gan@dell.com, yanxiu.cai@dell.com, libin.zhang@dell.com, ao.sun@dell.com Subject: Re: [PATCH v2 2/3] nvme-tcp: support specifying the congestion-control Message-ID: <20220314093429.00005b95@tom.com> In-Reply-To: <7121e4be-0e25-dd5f-9d29-0fb02cdbe8de@grimberg.me> References: <20220311103414.8255-1-sunmingbao@tom.com> <20220311103414.8255-2-sunmingbao@tom.com> <7121e4be-0e25-dd5f-9d29-0fb02cdbe8de@grimberg.me> X-Mailer: Claws Mail 3.18.0 (GTK+ 2.24.33; x86_64-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220313_183452_634044_10B41F84 X-CRM114-Status: GOOD ( 10.40 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org Before answering the questions, I=E2=80=99d like to address the motivation behind this patchset. You know, InfiniBand/RoCE provides NVMe-oF a lossless network environment (that is zero packet loss), which is a great advantage to performance. In contrast, 'TCP/IP + ethernet' is often used as a lossy network environment (packet dropping often occurs).=20 And once packet dropping occurs, timeout-retransmission would be triggered. But once timeout-retransmission was triggered, bandwidth would drop to 0 all of a sudden. This is great damage to performance. So although NVMe/TCP may have a bandwidth competitive to that of NVMe/RDMA, but the packet dropping of the former is a flaw to its performance. However, with the combination of the following conditions, NVMe/TCP can become much more competitive to NVMe/RDMA in the data center. - Ethernet NICs supporting QoS configuration (support mapping TOS/DSCP in IP header into priority, supporting adjusting buffer size of each priority, support PFC) - Ethernet Switches supporting ECN marking, supporting adjusting buffer size of each priority. - NVMe/TCP supports specifying the tos for its TCP traffic (already implemented) - NVMe/TCP supports specifying dctcp as the congestion-control of its TCP sockets (the work of this feature) So this feature is the last item from the software aspect to form up the above combination.