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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 68F42C47404 for ; Mon, 7 Oct 2019 22:22:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2947420835 for ; Mon, 7 Oct 2019 22:22:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728980AbfJGWWe (ORCPT ); Mon, 7 Oct 2019 18:22:34 -0400 Received: from mail-pf1-f195.google.com ([209.85.210.195]:37990 "EHLO mail-pf1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728654AbfJGWWe (ORCPT ); Mon, 7 Oct 2019 18:22:34 -0400 Received: by mail-pf1-f195.google.com with SMTP id h195so9546726pfe.5; Mon, 07 Oct 2019 15:22:33 -0700 (PDT) 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=PdkJ4Z+HzytIxudQqsDlaQKJxjFii3sZzUB2db98gvY=; b=ZJ71WyEP5XXMr+1aiGaBVryqG0NdieaiYHaC82iND4CyN9GpJd53Yw4fpivjtxh+0E OCdYe3U01uELX/6k650grCMVFJe32yudWjgh2eCFJe452kaEPiE/eKq+ioCDW9RpGozc 2UzhxRAlvoX/xtjqMkZ0/hlG5yP6rmTbRgALrKOUJLqpGEvWYo3bmAD6XSbiEpp/g3rz S7xQG11e0pA2dqAECRhP9OKjD7HX/Op/u9c1UPiDj0ja3/EriF8ORRoaVQ7NNj7ruCWr N9DRJaS0bUdI09YcAWPvdEewtJuJKL7SwmTtV8VBd1fFioXPIgw2RWLiOXUAEAjv3Js6 zzww== X-Gm-Message-State: APjAAAUjqk4Ia36ikopRuxutwgIBc8ZPn9WwQtpYHc21iCGtI3YiT1Sw LOa7r7doZb6yBq1rbSVSs1YFu/Ui X-Google-Smtp-Source: APXvYqzdKNwxtKOMAm1+Gvne26nJWbaDyd2nTTcmgg64eaPk+FXegTjIsKwG7jOyi1K3FyTqL5FOLw== X-Received: by 2002:a65:4785:: with SMTP id e5mr32267378pgs.407.1570486952364; Mon, 07 Oct 2019 15:22:32 -0700 (PDT) Received: from desktop-bart.svl.corp.google.com ([2620:15c:2cd:202:4308:52a3:24b6:2c60]) by smtp.gmail.com with ESMTPSA id b185sm16432284pfg.14.2019.10.07.15.22.30 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 07 Oct 2019 15:22:31 -0700 (PDT) Subject: Re: [PATCH rdma-next v2 2/3] RDMA/rw: Support threshold for registration vs scattering to local pages To: Leon Romanovsky Cc: Doug Ledford , Jason Gunthorpe , Christoph Hellwig , RDMA mailing list , Or Gerlitz , Yamin Friedman , Saeed Mahameed , linux-netdev References: <20191007135933.12483-1-leon@kernel.org> <20191007135933.12483-3-leon@kernel.org> <20191007160336.GB5855@unreal> From: Bart Van Assche Message-ID: <8d610a58-abb5-941a-2a52-96ab9287572b@acm.org> Date: Mon, 7 Oct 2019 15:22:30 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <20191007160336.GB5855@unreal> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-rdma-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rdma@vger.kernel.org On 10/7/19 9:03 AM, Leon Romanovsky wrote: > On Mon, Oct 07, 2019 at 08:07:55AM -0700, Bart Van Assche wrote: >> On 10/7/19 6:59 AM, Leon Romanovsky wrote: >>> /* >>> - * Check if the device might use memory registration. This is currently only >>> - * true for iWarp devices. In the future we can hopefully fine tune this based >>> - * on HCA driver input. >>> + * Check if the device might use memory registration. This is currently >>> + * true for iWarp devices and devices that have optimized SGL registration >>> + * logic. >>> */ >> >> The following sentence in the above comment looks confusing to me: "Check if >> the device might use memory registration." That sentence suggests that the >> HCA decides whether or not to use memory registration. Isn't it the RDMA R/W >> code that decides whether or not to use memory registration? > > I'm open for any reasonable text, what do you expect to be written there? Hi Leon, How about the following (not sure whether this is correct)? /* * Report whether memory registration should be used. Memory * registration must be used for iWarp devices because of * iWARP-specific limitations. Memory registration is also enabled if * registering memory will yield better performance than using multiple * SGE entries. */ Thanks, Bart.