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 079BFC742D2 for ; Fri, 12 Jul 2019 19:40:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D780F205C9 for ; Fri, 12 Jul 2019 19:40:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727125AbfGLTkJ (ORCPT ); Fri, 12 Jul 2019 15:40:09 -0400 Received: from mail-ot1-f65.google.com ([209.85.210.65]:33441 "EHLO mail-ot1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727226AbfGLTkI (ORCPT ); Fri, 12 Jul 2019 15:40:08 -0400 Received: by mail-ot1-f65.google.com with SMTP id q20so10576428otl.0; Fri, 12 Jul 2019 12:40:08 -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=HFpxZgsSIxsazA1/oZg/kAp/zrOjt6UHihSAZrgcZlE=; b=Ae4lZh/7hluwXWWoHAwv/UxbvQkZ3mhXQxISte0T+aLmWoht5y5eLA5RRW7CeodQlH SI+ZUvEgGUdsKBuwzaFPUYMXK+K7rmRz9c1LhGwaq6iULRHEBcAZwwAQyP1dPq8Dugyo QLsWegTKxfYgdbpsNkVn5oL2ozbB4diD7LIsmyfqfrDTZ3TKBUvJC+4bKPRf2ik2VVrs iOlPzlNC7k5RfbvDKgiVS47JFHvAVF4m+8ZeQ4bIBaXp0p622qG6wF1tzbAxCjI1CfWJ fT7AONZ63kfeOSpDbe/9xYNKj6C9n13U1Rs9WimJpidC8bPQzcOzIjYdjZ2dwmnryGcJ fjnQ== X-Gm-Message-State: APjAAAVIcNowOGg9Aa75mlf+YzTjZHfTZttQbuZ10/xGIv5VKN8OFO26 VyB1dqY5ta+uqKWgxGtltQ8= X-Google-Smtp-Source: APXvYqzveAK2peSCSmr6FwEGqa68OjQzEs78W1hOb+X3FP4XQUInf/BMTUhVYhWSQQweFrMPHqspLA== X-Received: by 2002:a05:6830:120e:: with SMTP id r14mr9497773otp.4.1562960407781; Fri, 12 Jul 2019 12:40:07 -0700 (PDT) Received: from ?IPv6:2600:1700:65a0:78e0:514:7862:1503:8e4d? ([2600:1700:65a0:78e0:514:7862:1503:8e4d]) by smtp.gmail.com with ESMTPSA id 68sm3380373otg.78.2019.07.12.12.40.06 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 12 Jul 2019 12:40:07 -0700 (PDT) Subject: Re: [PATCH v4 00/25] InfiniBand Transport (IBTRS) and Network Block Device (IBNBD) To: Jinpu Wang Cc: Danil Kipnis , linux-block@vger.kernel.org, linux-rdma@vger.kernel.org, Jens Axboe , Christoph Hellwig , bvanassche@acm.org, jgg@mellanox.com, dledford@redhat.com, Roman Pen , Greg Kroah-Hartman References: <20190620150337.7847-1-jinpuwang@gmail.com> From: Sagi Grimberg Message-ID: <11653912-924a-965a-45fe-3abd1ca00053@grimberg.me> Date: Fri, 12 Jul 2019 12:40:05 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org > Hi Sagi, > >>>> Another question, from what I understand from the code, the client >>>> always rdma_writes data on writes (with imm) from a remote pool of >>>> server buffers dedicated to it. Essentially all writes are immediate (no >>>> rdma reads ever). How is that different than using send wrs to a set of >>>> pre-posted recv buffers (like all others are doing)? Is it faster? >>> At the very beginning of the project we did some measurements and saw, >>> that it is faster. I'm not sure if this is still true >> >> Its not significantly faster (can't imagine why it would be). >> What could make a difference is probably the fact that you never >> do rdma reads for I/O writes which might be better. Also perhaps the >> fact that you normally don't wait for send completions before completing >> I/O (which is broken), and the fact that you batch recv operations. > > I don't know how do you come to the conclusion we don't wait for send > completion before completing IO. > > We do chain wr on successfull read request from server, see funtion > rdma_write_sg, I was referring to the client side